Manufacturing method of semiconductor apparatus and semiconductor apparatus

ABSTRACT

A screen oxide film is formed on an n− drift layer ( 2 ) that is disposed on an anterior side of an n-type low-resistance layer ( 1 ), and a nitride film is formed on the screen oxide film. The nitride film is photo-etched using a first mask and thereby, a nitride shielding film ( 61 ) is formed. N-type impurity ions at a concentration higher than that of the n-drift layer are implanted through the nitride shielding film ( 61 ) from an anterior side of a semiconductor substrate and are thermally diffused and thereby, an n counter layer ( 7 ) is formed. The screen oxide film is removed. A gate oxide film ( 3   a ) is formed. A gate electrode ( 9 ) is formed on the gate oxide film ( 3   a ). P-type impurity ions are implanted from the anterior side of the semiconductor substrate using the gate electrode ( 9 ) and the nitride shielding film ( 61 ) as a mask and thereby, p− well regions ( 10 ) are formed. N-type impurity ions are implanted from the anterior side of the semiconductor substrate using the gate electrode ( 9 ) and the nitride shielding film ( 61 ) as a mask and thereby, n source regions ( 11 ) are formed.

TECHNICAL FIELD

The present invention relates to a manufacturing method and asemiconductor apparatus of a vertical power semiconductor such as aMOSFET (Metal Oxide Semiconductor Field Effect Transistor) or an IGBT(Insulated Gate Bipolar Transistor).

BACKGROUND ART

Generally, semiconductor devices are classified as horizontal deviceshaving electrodes formed on one side of the semiconductor substrate, oras vertical devices having electrodes on both sides of the semiconductorsubstrate. In a vertical semiconductor device, the direction of flow ofa drift current when the device is turned on and the expansion directionof a depletion layer caused by a reverse bias voltage when the device isturned off are same.

A semiconductor indicated herein with “n” or “p” at the head means thatelectrons or holes are the majority carriers of the semiconductor. “⁺”or “−” that is appended to “n” or “p” like “n⁺” and “n⁻” represents arelatively higher concentration or a relatively lower concentration withrespect to an impurity concentration of a semiconductor that is notattached thereto.

FIG. 92 is a cross-sectional diagram of an active portion of aconventional planar n-channel MOSFET. As depicted in FIG. 92, theconventional planar n-channel vertical MOSFET 110 has an n⁻ drift layer2 that is disposed on an anterior side of an n-type low-resistance layer1. In a surface layer of the n⁻ drift layer 2, a p⁻ well region 10 isprovided. In a surface layer of the p⁻ well region 10, n source regions11 are selectively provided. Between the n source regions 11 in thesurface layer of the p⁻ well region 10, p-type high-concentrationregions 13 are disposed on a region sandwiched by the n source regions11 and the n⁻ drift layer 2 in the p⁻ well region 10, a gate electrode 9is provided through a gate insulating film 3 a. An inter-layerinsulating film 12 is disposed to cover the gate electrode 9. A sourceelectrode 14 is disposed to contact the n source region 11 and thep-type high-concentration region 13. The source electrode 14 isinsulated by the inter-layer insulating film 12 from the gate electrode9. A protective film 15 is disposed on the source electrode 14. A drainelectrode 16 is disposed on a posterior side of the n-typelow-resistance layer 1. In the conventional planar n-channel MOSFET, ann counter layer may be provided in the surface layer of the n⁻ driftlayer 2.

A manufacturing process of the conventional planar n-channel MOSFET willbe described. FIGS. 93 to 99 are diagrams for sequentially explainingthe manufacturing processes of the conventional planar n-channel MOSFET.As depicted in FIG. 93, for the conventional planar n-channel MOSFET,the n⁻ drift layer 2 is first formed by, for example, epitaxial growthon the anterior side of the n-type low-resistance layer 1. Thesemiconductor substrate having the n⁻ drift layer 2 formed on theanterior side of the n-type low-resistance layer 1 is referred to as“semiconductor substrate”. The gate insulating film 3 a is formed on then⁻ drift layer 2. Conductive poly-silicon 8 is deposited on the gateinsulating film 3 a. The n counter layer may be formed by implantingboron ions into the surface of the n⁻ drift layer 2.

As depicted in FIG. 94, the gate insulating film 3 a and thepoly-silicon 8 are etched using a first mask not depicted and formed bypattern-forming with a resist film and thereby, the gate electrode 9 isformed. After removing the first mask, using the gate electrode 9 as amask, impurity ions are implanted into the regions having the n⁻ driftlayer 2 exposed therein and thereby, the p⁻ well region 10 is formed.

As depicted in FIG. 95, impurity ions are implanted into an opening 82of a second mask 81 formed by pattern-forming with a resist film andthereby, a p-type high-concentration region 13 is formed in the surfacelayer of the p⁻ well region 10. The second mask 81 is formed such thatthe edge of the opening 82 is about 0.5 to 2.0 micrometers away from thegate electrode 9. As depicted in FIG. 96, the second mask 81 is removed.

As depicted in FIG. 97, a third mask 83 is formed by pattern-formingwith a resist film and ion implantation is executed using the gateelectrode 9 and the third mask 83 as a mask and thereby, the n sourcelayers 11 are selectively formed in the surface layer of the p-typehigh-concentration region 13. As depicted in FIG. 98, the third mask 83is removed.

At this time, a surface along a long side of a region sandwiched by then source regions 11 and the n⁻ drift layer 2 of the p⁻ well region 10 isa channel region. The channel region is a region of an inversion layerthat is formed in the surface layer of the p⁻ well region 10 when a gatevoltage equal to or higher than a threshold voltage is applied to thegate electrode 9.

The insulating layer 12 is deposited from the anterior side of thesemiconductor substrate. Using a fourth mask not depicted formed bypattern-forming with a resist film, the insulating film 12 isselectively removed not to expose the gate electrode 9 and thereby,openings 85 are formed. Therefore, in the openings 85, the p-typehigh-concentration region 13 and the n source regions 11 are exposed.

As depicted in FIG. 99, the source electrode (Al—Si) 14 is formed tocommonly contact the p-type high-concentration region 13 and the nsource regions 11 in the openings 85. The protective film 15 is formedon the source electrode 14 and the drain electrode 16 is formed on theposterior side of the semiconductor substrate. Thereby, the planarn-channel MOSFET is completed.

However, according to the manufacturing method of the conventionalplanar n-channel MOSFET, one mask is used in each one ion implantingsession. Therefore, to manufacture the planar n-channel MOSFET, fourmasks in total, the first to the fourth masks, are necessary. Asdescribed, when many pattern-forming sessions for masks are executed,the number of processes becomes large and therefore, the cost for themanufacture becomes high. When the number of sessions that use masks islarge, the alignment precision is degraded and therefore, the toleranceto variation among devices must be increased. Therefore, finerprocessing becomes difficult. Heat treatment is applied twice betweenthe formation of the gate electrode using the first mask and theformation of the inter-layer insulating film and therefore, loads areapplied to the gate film.

To solve these problems, a method has been proposed of forming thesource region and the drain region using the same mask when a horizontalsemiconductor device is formed (see, e.g., Patent Document 1). Thesource region and the drain region of the horizontal semiconductordevice: are both formed on the anterior side of a semiconductorsubstrate; are of the same conductivity; have the same impurityconcentration; and therefore, may simultaneously be formed. However, ina vertical semiconductor device, the source region and the drain regionare formed separately from each other on respective sides of asemiconductor substrate. Therefore, this method can not be applied tothe vertical semiconductor device.

Thus, for the vertical semiconductor device, a method has been proposedof forming the p⁻ well region 10 and the n source region 11 using thesame nitride film (Si₃N₄) mask after forming the gate electrode 9 (see,e.g., Patent Document 2). According to this method, to form a LOCOS(Local Oxidation of Silicon) oxide film to be used as a mask when thep-type high-concentration region 13 is formed after the n source region11 is formed, selective oxidation is executed using a nitride film maskand thereby, an oxide film is thickly formed in a region having nonitride film mask formed therein on the anterior side of thesemiconductor substrate. Patterning is executed for this oxide film andthereby, the LOCOS oxide film to be used as the mask is formed.

A voltage-resistant structure portion of the conventional planarn-channel MOSFET will be described. A guard ring technique will bedescribed that is one of voltage-resistant structure techniques for asemiconductor apparatus. FIG. 100 is a diagram for explaining thecross-sectional structure of the voltage-resistant structure portion ofthe conventional planar n-channel MOSFET. FIG. 101 is a diagram forexplaining in detail the cross-sectional structure of active portionvicinity 211 of a voltage-resistant structure portion 210 of theconventional planar n-channel MOSFET. As depicted in FIG. 100, thevoltage-resistant structure portion 210 of the conventional planarn-channel MOSFET is disposed on the outer edge of the active portion110. The voltage-resistant structure portion 210 is provided with aloop-shaped p⁻ region 10 b in the surface layer of the n⁻ drift layer 2such that the p⁻ region 10 b surrounds the p⁻ well region 10. The p⁻region 10 b is connected to the p⁻ well region 10. The impurityconcentration of the p⁻ region 10 b is lower than the impurityconcentration of the p⁻ well region 10. The diffusion depth of the p⁻region 10 b is deeper than the diffusion depth of the p⁻ well region 10.A p guard ring 10 c is provided in a loop shape to surround the p⁻region 10 b. An end of the p guard ring 10 c is connected to an edge ofthe p⁻ region 10 b. The impurity concentration of the p guard ring 10 cis equal to the impurity concentration of the p⁻ region 10 b. Thediffusion depth of the p guard ring 10 c is equal to the diffusion depthof the p⁻ region 10 b (see, e.g., Patent Document 3). Thevoltage-resistant structure is configured by employing a semiconductorapparatus configuration formed by combining a RESURF (REduced SURfaceField) structure and a guard ring (field-limiting ring) structure,without using any field plate that reduces the conductivity at a lowtemperature, as the technique described in Patent Document 3.

As depicted in FIG. 101, an outer edge of the active portion 110 isselectively provided with p-type high-concentration regions 13 in thesurface layer of the p⁻ well region 10. The gate electrode 9 is providedthrough the gate insulating film 3 a on a region sandwiched by thep-type high-concentration regions 13 and the n⁻ drift layer 2 of the pwell region 10. Other configurations on the outer edge of the activeportion 110 are same as those of the active portion 110 of thesemiconductor apparatus depicted in FIG. 92.

A surface layer of the p guard ring 10 c is selectively provided withthe p⁻ well regions 10. Field plate electrodes 9 a are selectivelyprovided through an insulating film 25 on the p⁻ region 10 b and the pguard ring 10 c. An opening is provided for the insulating film 25. Theopening has exposed therein the p⁻ well regions 10 that are provided forthe surface layer of the p guard ring 10 c. Inter-layer insulating films19 are selectively disposed on the surface of the field plate electrodes9 a such that a portion of each of the field plate electrodes 9 a isexposed. A metal film 14 a is disposed to contact the field plateelectrodes 9 a and the p⁻ well region 10 that is exposed in the openingof the insulating film 25. The protective film 15 is disposed on thesource electrode 14 and the metal film 14 a. The drain electrode 16 isdisposed on the posterior side of the n-type low-resistance layer 1.

In the planar structure not depicted of the chip having the activeportion and the voltage-resistant structure portion of the conventionalplanar n-channel MOSFET, the active portion 110 is provided in thecentral portion of the chip and the voltage-resistant structure portion210 is disposed on the outer circumference of the active portion 110. Ap stopper region 77, a p contact region 73, and a contact opening 76 ofthe voltage-resistant structure portion 210 (see FIG. 100) are disposedon the entire circumference of the voltage-resistant structure portionto surround the p guard ring 10 c on the outer circumference of thechip.

Manufacturing processes of the guard ring of the conventional planarn-channel MOSFET will be described. FIGS. 102 to 110 are diagrams forsequentially explaining the manufacturing processes of the guard ring ofthe conventional planar n-channel MOSFET. As depicted in FIG. 102, forthe voltage-resistant structure portion of the conventional planarn-channel MOSFET, an insulating film 24 is formed on the semiconductorsubstrate on which the n⁻ drift layer 2 is formed by, for example,epitaxial growth on the anterior side of the n-type low-resistance layer1. As depicted in FIG. 103, the insulating film 24 is etched using asixth mask not depicted and formed by pattern-forming with a resist filmusing a photo-mask and thereby, the surface of the n drift layer 2 isselectively exposed.

Using the insulating film 24 as a mask, impurity ions are implanted intothe regions having the n⁻ drift layer 2 exposed therein and thereby, thep⁻ region 10 b and the p guard ring 10 c are formed. As depicted in FIG.104, leaving the insulating film 24 as it is, the entire anterior faceof the semiconductor substrate is oxidized and thereby, an insulatingfilm 25 is formed. As depicted in FIG. 105, the insulating film 25 isetched using a seventh mask not depicted and formed by pattern-formingwith a resist film using a photo-mask and thereby, the surface of the n⁻drift layer 2 and a portion of the surface of the p guard ring 10 c areselectively exposed.

As depicted in FIG. 106, the gate insulating film 3 a is formed on theanterior side of the semiconductor substrate and the conductivepoly-silicon 8 is deposited on the gate insulating film 3 a. As depictedin FIG. 107, the gate insulating film 3 a and the poly-silicon 8 areetched using an eighth mask not depicted and formed by pattern-formingwith a resist film using a photo-mask and thereby, the gate electrode 9and the field plate electrode 9 a are formed. After removing the eighthmask, impurity ions are implanted into the regions having the n⁻ driftlayer 2 exposed therein using the gate electrode 9 and the insultingfilm 25 as a mask and thereby, the p⁻ well region 10 is formed.Simultaneously, impurity ions are implanted into the region having the pguard ring 10 c exposed therein using the gate electrode 9 and the fieldplate electrode 9 a as a mask and thereby, the p⁻ well region 10 isformed.

As depicted in FIG. 108, impurity ions are implanted into an opening 86of a ninth mask 301 formed by pattern-forming with a resist film using aphoto-mask and thereby, the p-type high-concentration region 13 isformed in the surface layer of the p⁻ well region 10. At this time, theninth mask 301 is formed such that the edge of the opening 86 is about0.5 to 2.0 micrometers away from the gate electrode 9.

As depicted in FIG. 109, the ninth mask 301 is removed and an insulatingfilm is deposited from the anterior side of the semiconductor substrate.Using a tenth mask not depicted and formed by pattern-forming with aresist film using a photo-mask, the insulating film is selectivelyremoved such that the gate electrode 9 is not exposed and the fieldplate electrode 9 a is partially exposed and thereby, openings 87 and 88are formed. Thereby, the insulting film 12 is formed to cover the gateelectrode 9 and the insulating film 19 is formed such that the fieldplate electrode 9 a is partially exposed. The p-type high-concentrationregion 13 is exposed in the opening 87, and the p⁻ well region 10 isexposed in the opening 88.

As depicted in FIG. 110, the source electrode (Al—Si) 14 is formed to beelectrically connected in the opening 87 to the p⁻ well region 10through the p-type high-concentration region 13. The metal film (Al—Si)14 a is formed to contact the p⁻ well region 10 in the opening 88. Theprotective film 15 is formed on the source electrode 14 and the metalfilm 14 a and the drain electrode 16 is formed on the posterior side ofthe semiconductor substrate and thereby, the guard ring of the planarn-channel MOSFET as depicted in FIG. 101 is completed.

CITATION LIST Patent Literature

[PTL 1]

-   Japanese Laid-Open Patent Publication No. H1-289168    [PTL 2]-   Japanese Laid-Open Patent Publication No. H1-105578    [PTL 3]-   Japanese Laid-Open Patent Publication No. 2009-38356

SUMMARY OF INVENTION Technical Problem

However, in the technique of Patent Document 2, a problem arises in thatthe resistance of the top surface of the n source region is increased bythe oxidation executed when the LOCOS oxide film is formed that is usedas the mask to form the p-type high-concentration region. Because thisoxidation is executed after forming gate electrode 9, the gate electrode9 itself is oxidized. In addition, the lower portion of the gateinsulating film is oxidized and thereby, the gate electrode becomesthick and bird's beaks are produced. Therefore, another problem arisesin that the controllability of the threshold value of the MOSFET isdegraded.

According to the technique of Patent Document 3, the impurityconcentration of the p guard ring 10 c in the voltage-resistantstructure portion is lower than that of the p⁻ well region 10 in theactive portion. Therefore, ion implantation to form the p⁻ well region10 and that to form the p guard ring 10 c must be conducted separatelyfrom each other. Therefore, another problem arises in that themanufacturing cost is increased. In this case, for example, when ionimplantation is simultaneously executed for the p guard ring 10 c usingan ordinary impurity amount of about 1*10¹⁴ that is used to form the p⁻well region 10 of the active portion, the p guard ring 10 c issubstantially not depleted. Therefore, the length of the edge of the pguard ring 10 c must be extended and therefore, the chip size increases.Therefore, another problem arises in that the manufacturing costincreases.

According to the manufacturing method of the guard ring of theconventional planar n-channel MOSFET (see FIGS. 102 to 110), one mask isused in one ion implanting session similarly to the manufacture of theactive portion (see FIGS. 93 to 99). Therefore, as described, when thefive masks in total, the sixth to the tenth masks, are used, the fivephoto-masks are also necessary for exposing the masks with the patterns.Photo-masks are further necessary in processes such as the process ofseparating the electrodes by patterning the metal film that is formedinto the source electrode 14 and the metal film 14 a and the process ofcausing wires to contact the electrodes covered by the protective film.As described, similarly to the problems arising in the manufacture ofthe active portion, problems arise in that the manufacturing costincreases due to the increase in the number of processes, and in thatmask alignment errors caused in pattern-exposing sessions are compoundeddue to the large number of sessions that each use a photo-mask andthereby, the alignment precision is degraded and therefore, thetolerance to variation among devices must be increased.

To solve the above problems associated with the conventional techniques,an object of the present invention is to provide a manufacturing methodof a semiconductor apparatus and a semiconductor apparatus capable ofcontrolling manufacturing cost and reducing manufacture variation.Another object of the present invention is to provide a manufacturingmethod of a semiconductor apparatus and a semiconductor apparatuscapable of facilitating finer processing of the semiconductor apparatus.

Solution to Problem

To solve the problems associated with the conventional arts, asemiconductor apparatus manufacturing method according to a first aspectof the invention includes selectively forming a shielding film in asurface layer on an anterior side of a first semiconductor region of afirst conductivity; forming a control electrode through a firstinsulating film on the first semiconductor region, apart from theshielding film; forming a second semiconductor region of a secondconductivity in a surface layer of the first semiconductor region usingthe shielding film and the control electrode as a mask and selectivelyforming a third semiconductor region of the first conductivity in asurface layer of the second semiconductor region using again theshielding film and the control electrode as the mask; forming a secondinsulating film to cover the control electrode and removing theshielding film; forming a first electrode to contact the thirdsemiconductor region and to be insulated from the control electrode bythe second insulating film; and forming a second electrode on aposterior side of the first semiconductor region. The control electrodeis formed through the first insulating film on a surface of the secondsemiconductor region that is sandwiched by the first semiconductorregion and the third semiconductor region.

A semiconductor apparatus manufacturing method according to the firstaspect of the invention may further include forming a counter region ofthe first conductivity in the surface layer of the first semiconductorregion by implanting, through the shielding film, impurity ions of thefirst conductivity at an impurity concentration greater than that of thefirst semiconductor region, the counter region being formed afterforming the shielding film. The second semiconductor region is formed ina surface layer of the counter region in the first semiconductor region,and the control electrode is formed through the first insulating film onthe surface of the second semiconductor region that is sandwiched by thecounter region in the first semiconductor region and the thirdsemiconductor region.

The shielding film may be formed using a nitride film.

The shielding film may be formed using an oxide film produced bychemical vapor deposition.

The shielding film may be formed using an oxide film produced by thermaloxidation.

The shielding film may be formed such that at least a portion of theshielding film is disposed immediately beneath the control electrode,and at the removing the shielding film, the portion of the shieldingfilm disposed immediately beneath the control electrode is not removed.

The shielding film may be formed such that the portion of the shieldingfilm is disposed immediately beneath the control electrode and does notreach any edge of the second semiconductor region.

The shielding film may be formed such that the portion of the shieldingfilm is disposed immediately beneath the control electrode and reachesan edge of the second semiconductor region.

A high concentration region of the second conductivity may be formed byimplanting impurity ions of the second conductivity at approximately anaccelerating voltage for the impurity ions to penetrate the thirdsemiconductor region, from the surface layer of the second semiconductorregion using the second insulating film as a mask, after forming thesecond insulating film and removing the shielding film.

A semiconductor apparatus manufacturing method according to a secondaspect of the invention includes forming a control electrode through afirst insulating film in a surface layer on an anterior side of a firstsemiconductor region of a first conductivity and forming a shieldingfilm such that a region between the shielding film and the controlelectrode is a region to form a third semiconductor region of the firstconductivity; forming a second semiconductor region of a secondconductivity in a surface layer of the first semiconductor region usingthe shielding film and the control electrode as a mask and selectivelyforming a third semiconductor region in a surface layer of the secondsemiconductor region using again the shielding film and the controlelectrode as the mask; forming a second insulating film to cover thecontrol electrode and removing the shielding film; forming a firstelectrode to contact the third semiconductor region and to be insulatedfrom the control electrode by the second insulating film; and forming asecond electrode on a posterior side of the first semiconductor region.The control electrode is formed through the first insulating film on asurface of the second semiconductor region that is sandwiched by thefirst semiconductor region and the third semiconductor region.

In the semiconductor apparatus manufacturing method according to secondaspect of the invention, at the forming the second insulating film andremoving the shielding film, a portion of the shielding film may be lefton the second insulating film.

The semiconductor apparatus manufacturing method according to the secondaspect of the invention may further include forming a high concentrationregion of the second conductivity by implanting impurity ions of thesecond conductivity at approximately an accelerating voltage for theimpurity ions to penetrate the third semiconductor region, from thesurface layer of the second semiconductor region using the secondinsulating film as a mask, after forming the second insulating film andremoving the shielding film.

At the forming the high concentration region of the second conductivity,regions where the high concentration region of the second conductivityis exposed and is not exposed on a surface of the second semiconductorregion may be formed using a common mask.

The region where the high concentration region of the secondconductivity that is not exposed on the surface of the secondsemiconductor region may be formed at one point in each line portion ofa stripe-shaped planar structure that is formed by the region where thehigh concentration region of the second conductivity is exposed on thesurface of the second semiconductor region.

The region where the high concentration region of the secondconductivity that is not exposed on the surface of the secondsemiconductor region may be formed at a plurality of points in each lineportion of a stripe-shaped planar structure that is formed by the regionwhere the high concentration region of the second conductivity isexposed on the surface of the second semiconductor region.

The region where the high concentration region of the secondconductivity that is not exposed on the surface of the secondsemiconductor region may be formed at staggered positions in each lineportion of a stripe-shaped planar structure that is formed by the regionwhere the high concentration region of the second conductivity isexposed on the surface of the second semiconductor region.

A semiconductor apparatus manufacturing method according to a thirdaspect of the invention is characterized in that the nitride film isformed on the surface layer on the anterior side of the firstsemiconductor region of the first conductivity. Openings are selectivelyformed in the nitride film and the surface layer is exposed in theopenings. Impurity ions of the second conductivity at a relatively lowimpurity concentration are implanted into the openings and thereby, thesecond semiconductor region of the second conductivity is formed. Theoxide films are formed in the openings as shielding films by thermaloxidation. The nitride film is removed. Impurity ions of the secondconductivity at an impurity concentration higher than that of the secondsemiconductor region are implanted using the shielding film as a maskand thereby, the second-conductivity surface region is formed. On thesecond semiconductor region, a control electrode is formed through thefirst insulating film. Impurity ions of the first conductivity areimplanted using the shielding film and the control electrode as a maskand thereby, the third semiconductor region of the first conductivity isformed. The second insulating film is formed to cover the controlelectrode and, after the shielding film is removed, the first electrodeis formed to contact the third semiconductor region and to be insulatedfrom the control electrode by the second insulating film. The secondelectrode is formed on the posterior side of the first semiconductorregion. The expression “the impurity concentration is high” used hereinexpresses the same meaning as that of the expression “the impurityconcentration is thick”.

A semiconductor apparatus manufacturing method according to a fourthaspect of the invention is characterized in that impurity ions of afirst conductivity at an impurity concentration greater than that of afirst semiconductor region are implanted into a surface layer on theanterior side of the first semiconductor region of the firstconductivity and thereby, a counter region of the first conductivity isformed in the surface layer of the first semiconductor region. A nitridefilm is formed on the entire counter region, openings are selectivelyformed in the nitride film, and the counter region is exposed in theopenings. Impurity ions of the second conductivity at a relatively lowimpurity concentration are implanted into the openings and thereby, thesecond semiconductor regions of the second conductivity are formed.Oxide films are formed on the openings as shielding films by thermaloxidation. The nitride film is removed. Impurity ions of the secondconductivity at an impurity concentration higher than that of the secondsemiconductor region are implanted using the shielding film as a maskand thereby, the second-conductivity surface region is formed. A controlelectrode is formed through a first insulating film on the secondsemiconductor region and on the counter region. A third semiconductorregion of the first conductivity is formed by implanting impurity ionsof the first conductivity using the shielding film and the controlelectrode as a mask. A second insulating film is formed to cover thecontrol electrode and the shielding film is removed. A first electrodeis formed to contact the third semiconductor region and to be insulatedfrom the control electrode by the second insulating film. A secondelectrode is formed on a posterior side of the first semiconductorregion.

A semiconductor apparatus manufacturing method according to the fourthaspect of the invention, for which the active portion of thesemiconductor apparatus formed according to the proceeding paragraph issimultaneously formed together with a voltage-resistant structureportion that surrounds the active portion, may further include formingan insulating film mask in the surface layer of the anterior side of thefirst semiconductor region of the first conductivity; forming insulatingfilm openings in a loop or a dot-shape to surround the active portion,in the insulating film mask; selectively forming a counter region of thefirst conductivity in the surface layer of the first semiconductorregion by implanting impurity ions of the first conductivity at animpurity concentration that is greater than that of the firstsemiconductor region into the insulating film openings; forming anitride film on insulating film mask and the counter region; selectivelyforming openings in the nitride film and exposing the counter region inthe openings; forming a second semiconductor region of a secondconductivity by implanting impurity ions of the second conductivity at arelatively low impurity concentration into the openings so that anadjacent second semiconductor region of the second conductivity becomejoined by diffusion; forming an oxide film as a shielding film in eachof the openings by thermal oxidation; removing the nitride film; forminga second-conductivity surface region by implanting impurity ions of thesecond conductivity at an impurity concentration that is higher thanthat of the second semiconductor region using insulating film mask andthe shielding film as a mask; forming a control electrode through afirst insulating film on the second semiconductor region and on aportion of the shielding film; forming a third semiconductor region ofthe first conductivity by implanting impurity ions of the firstconductivity using the shielding film and the control electrode as amask so that the control electrode is not covered; forming a secondinsulating film to expose a portion of the control electrode andremoving the shielding film; and forming a first electrode to contactthe third semiconductor region and a portion of the control electrodenot covered by the second insulating film.

In the voltage-resistant structure portion, the width of the openingformed in the nitride film may be narrower than a width of the openingformed in the nitride film in the active portion.

A high concentration region of the second conductivity may be formed byimplanting impurity ions of the second conductivity at a relatively highimpurity concentration into the opening used when the secondsemiconductor region is formed, the high concentration region beingformed after forming the second semiconductor region.

A semiconductor apparatus manufacturing method according to a fifthaspect of the invention is a manufacturing method of a semiconductorapparatus selectively formed to have second semiconductor regions of asecond conductivity in a surface layer on an anterior side of a firstsemiconductor region of a first conductivity, where a voltage-resistantstructure portion surrounding an active portion of the semiconductorapparatus is simultaneously formed when the active portion is formed.The method includes forming a shielding film in the surface layer on theanterior side of the first semiconductor region; forming a plurality ofshielding openings each in a loop to surround the active portion in theshielding film; forming a fifth semiconductor region of the secondconductivity that surrounds the active portion, a sixth semiconductorregion of the second conductivity that surrounds the fifth semiconductorregion, and a seventh semiconductor region of the second conductivitythat surrounds the sixth semiconductor region by implanting anddiffusing impurity ions of the second conductivity into the surfacelayer of the first semiconductor region through the shielding filmopenings; forming first local oxide films in surface layers of thefifth, the sixth, and the seventh semiconductor regions exposed in theshielding openings; selectively removing the shielding film afterforming the first local oxide films; forming second local oxide films inthe surface layers of the fifth, the sixth, and the seventhsemiconductor regions exposed between the shielding film and the firstlocal oxide films; selectively removing the shielding film after formingthe second local oxide films; forming a control electrode through thefirst insulating film on the first semiconductor region, forming a firstconducting layer through the first local oxide film on the sixthsemiconductor region, and forming a second conductive layer through thesecond local oxide film on the seventh semiconductor region apart fromthe first conductive layer; forming, in an outermost circumference ofthe active portion, a second semiconductor region in the surface layerof the first semiconductor region using the control electrode and thesecond local oxide films as a mask, and selectively forming a thirdsemiconductor region of the first conductivity in a surface layer of thesecond semiconductor region again using the control electrode and thesecond local oxide films as a mask; forming a second insulating film tocover the control electrode, selectively forming a third insulating filmon surfaces of the first and the second conductive layers, andselectively removing the second local oxide films; forming a firstelectrode to contact the third semiconductor region and to be insulatedby the second insulating film from the control electrode, and forming athird electrode that contacts the second conductive layer; and forming asecond electrode on a posterior side of the first semiconductor region.

The second conductive layer or an end of the third electrode on anactive portion side thereof that contacts the second conductive layermay be formed to cover a portion of the sixth semiconductor region.

The semiconductor apparatus manufacturing method according to the fifthaspect of the invention may further include forming a counter region ofthe first conductivity in the surface layer of the first semiconductorregion by implanting impurity ions of the first conductivity at animpurity concentration higher than that of the first semiconductorregion using the first and the second local oxide films, where thesecond semiconductor region is formed in a surface layer of the counterregion in the first semiconductor region, and the control electrode isformed through the first insulating film on a surface of the secondsemiconductor region that is sandwiched by the counter region in thefirst semiconductor region and the third semiconductor region.

A semiconductor apparatus manufacturing method according to the fifthaspect of the invention may further include forming a high concentrationregion of the second conductivity by implanting impurity ions of thesecond conductivity at an impurity concentration higher than that of thesecond semiconductor region into a surface layer of the fifth and theseventh semiconductor regions exposed, using the first local oxide filmsand the second and the third insulating films, where the highconcentration region of the second conductivity is formed after formingthe second and the third insulating films and selectively removing thesecond local oxide films.

The second and the third semiconductor regions may be formed on an innercircumference of the active portion, sequentially in the surface layerof the first semiconductor region by again using the shielding film andthe control electrode as masks.

The shielding film may be formed using a nitride film.

The first and the second conductive layers may be formed usingsemiconductors.

Impurities of the first conductivity may be introduced into the firstand the second conductive layers.

The first conductive layer may be formed as a semiconductor layer intowhich impurities of the first conductivity are introduced and the secondconductive layer may be formed as a metal layer.

Impurities of the first conductivity may be introduced into the controlelectrode.

A first-conductivity low-resistance layer may be provided between thefirst semiconductor region and the second electrode.

A fourth semiconductor region of the second conductive type may beprovided between the first semiconductor region and the secondelectrode.

A semiconductor apparatus according to a sixth aspect of the inventionis provided with an active portion and a voltage-resistant structureportion that surrounds the active portion on a same semiconductorsubstrate and includes a first semiconductor region of a firstconductivity; a second semiconductor region of a second conductivityselectively provided in a surface layer on an anterior side of the firstsemiconductor region; a third semiconductor region of the firstconductivity selectively provided in a surface layer of the secondsemiconductor region; a control electrode that is provided, through afirst insulating film, on a surface of the second semiconductor regionsandwiched by the first and the third semiconductor regions; a secondinsulating film that covers the control electrode; a first electrodethat contacts the third semiconductor region and is insulated by thesecond insulating film from the control electrode; a second electrodethat is disposed on a posterior side of the first semiconductor region;a fifth semiconductor region of the second conductivity at an impurityconcentration higher than that of the first semiconductor region andlower than that of the second semiconductor region, the fifthsemiconductor region of the second conductivity contacting andsurrounding the second semiconductor region, and provided at a depthdeeper than that of the second semiconductor region; a sixthsemiconductor region of the second conductivity at an impurityconcentration substantially equivalent to that of the fifthsemiconductor region, the sixth semiconductor region of the secondconductivity contacting and surrounding the fifth semiconductor region,and provided at a depth substantially equivalent to that of the fifthsemiconductor region; a seventh semiconductor region of the secondconductivity at an impurity concentration substantially equivalent tothat of the fifth semiconductor region, the seventh semiconductor regionof the second conductivity contacting and surrounding the sixthsemiconductor region, and provided at a depth substantially equivalentto that of the fifth semiconductor region; a first local oxide film thatis selectively provided in surface layers of the fifth, the sixth, andthe seventh semiconductor regions; a second local oxide film that isselectively provided in surface layers of the fifth, the sixth, and theseventh semiconductor regions, and contacts the first local oxide film;a first conducting layer that is provided through the first local oxidefilm on the sixth semiconductor region; a second conductive layer thatis provided through the second local oxide film on the seventhsemiconductor region apart from the first conductive layer; a thirdinsulating film that is selectively disposed on surfaces of the firstand the second conductive layers; and a third electrode that contactsthe second conductive layer. Further, the first conducting layer isdisposed to have a loop shape; the second conductive layer is disposedto have a loop shape that surrounds the first conductive layer; and thesecond conductive layer or an end of the third electrode on an activeportion side thereof contacting the second conductive layer is disposedto cover a portion of the sixth semiconductor region.

A semiconductor apparatus according to the sixth aspect of the inventionmay further include a counter region of the first conductivity that isprovided in the surface layer of the first semiconductor region, wherethe second semiconductor region is provided in a surface layer of thecounter region in the first semiconductor region, and the controlelectrode is provided through the first insulating film, on a surface ofthe second semiconductor region that is sandwiched by the counter regionin the first semiconductor region and the third semiconductor region.

A semiconductor apparatus according to the sixth aspect of the inventionmay further include a high concentration region of the secondconductivity provided in surface layers of the fifth and the seventhsemiconductor regions, and having an impurity concentration that ishigher than that of the second semiconductor region.

The first and the second conducting layers may be conductivesemiconductor layers to which impurities of the first conductivity areadded.

The first conductive layer may be a conductive semiconductor layer towhich impurities of the first conductivity are added and the secondconductive layer may be a metal layer.

The control electrode may be a conductive semiconductor layer to whichimpurities of the first conductivity are added and the second conductivelayer may be a metal layer.

A first-conductivity low-resistance layer may be provided between thefirst semiconductor region and the second electrode.

A fourth semiconductor region of the second conductivity may be providedbetween the first semiconductor region and the second electrode.

According to the first aspect of the invention and its refinements, thesecond semiconductor region of the second conductivity and the thirdsemiconductor region of the first conductivity may be formed using theshielding film and the control electrode as a common mask. Morespecifically, for example, in a planar MOSFET, ions can be implantedinto a p⁻ well region and an n source region using the common mask.Therefore, pattern formation with a resist film can be omitted forforming each of the p⁻ well region and the n source region. Therefore,one process of executing pattern formation with a mask by photo-etchingcan be omitted and therefore, the manufacturing cost can be reduced.When the number of sessions each using a different mask is large,variation caused during the manufacture is highly likely to begenerated. However, the number of masks used in the manufacturingprocesses can be reduced by one and therefore, the variation causedduring the manufacture can be suppressed to the extent influenced by theone mask.

According to the second aspect of the invention and its refinements, thesecond semiconductor region of the second conductivity and the thirdsemiconductor region of the first conductivity can be formed using theshielding film and the control electrode as common masks. The shieldingfilm and the control electrode can be formed using a same mask.Therefore, two processes each of executing the pattern formation for themask by photo-etching can be omitted. Therefore, the manufacturing costcan be reduced. Two of the masks used in the manufacturing processes canbe omitted and therefore, the variation caused during the manufacturecan be suppressed to the extent influenced by the two masks.

According to the third and fourth aspects of the invention, the secondsemiconductor region of the second conductivity can be formed using themask to form the shielding film. The shielding film can be formed usingthis mask. Therefore, one process of executing the pattern formation forthe mask by photo-etching can be omitted. Therefore, the manufacturingcost can be reduced. One of the masks used in the manufacturingprocesses can be omitted and therefore, the variation caused during themanufacture can be suppressed to the extent influenced by the one mask.

According to one of the refinements of the fourth aspect, when the ionsare implanted into the second semiconductor region of the secondconductivity of the active portion, the ion implantation cansimultaneously be executed into the guard ring of the voltage-resistantstructure portion. Therefore, in the case where the active portion andthe voltage-resistant structure portion are simultaneously formed, whenthe second semiconductor region of the second semiconductor type of theactive portion is formed, the guard ring of the voltage resistantstructure portion can be formed using the common mask. Therefore, oneprocess of executing the pattern formation for the mask by photo-etchingcan be omitted. Therefore, the manufacturing cost can be reduced.

According to the fifth aspect of the invention and its refinements, whenthe voltage resistant structure portion is formed simultaneously withthe active portion, the second semiconductor region of the secondconductivity and the third semiconductor region of the firstconductivity can be formed using the second local oxide film and thecontrol electrode as the common masks. More specifically, for example,for a planar MOSFET, ion implantation can be executed for the p⁻ wellregion and the n source region using a common mask. Therefore, in theactive portion, pattern formation with a resist film using a photo-maskcan be omitted for forming each of the p well region and the n sourceregion. Therefore, in the active portion, one process of executingpattern formation for a mask by photo-etching can be omitted and,associated with this, in the voltage resistant structure portionsimultaneously formed, one process of executing pattern formation for amask by photo-etching can be omitted. Thereby, the manufacturing costfor forming the voltage resistant structure portion can be reduced. Whenthe number of sessions each using a different mask is large, variationcaused during the manufacture is highly likely to be generated due tothe degradation of the alignment precision caused by accumulation ofmask alignment errors of the exposing sessions of the patterns. However,one of the masks used in the manufacturing processes can be omitted andtherefore, the manufacture variation can be suppressed to the extent ofthe influence of the one mask. In the voltage resistant structureportion, an end of the second conductive layer on its active portionside is formed to cover the portion of the sixth semiconductor region inthe region having the sixth and the seventh semiconductor regionscontacting each other, through the second local oxide film. In thesemiconductor apparatus having the above configuration, the electricalfield is mitigated in the p-n junction region that is configured by thesixth and the first semiconductor regions. Therefore, the electric fieldintensity can be reduced that is generated in the semiconductorsubstrate when the semiconductor apparatus is turned on. Thereby, evenwhen finer processing of the semiconductor apparatus is facilitated, thesame voltage resistance as that of the conventional semiconductorapparatus can be maintained. By reducing the number of masks, thealignment of the device is improved relative to that of the conventionaldevice. Only one heat treatment session is executed after forming thegate electrode and therefore, production of bird's beaks can beprevented.

According to the sixth aspect of the invention and its refinements, inthe voltage resistant structure portion, the end of the secondconductive layer on its active portion side is formed to cover theportion of the sixth semiconductor region in the region having the sixthand the seventh semiconductor regions contacting each other through thesecond local oxide film. Thereby, the electrical field can be mitigatedin the p-n junction region that is configured by the sixth and the firstsemiconductor regions. Therefore, the electric field intensity can bereduced that is generated in the semiconductor substrate when thesemiconductor apparatus is turned on. Thereby, even when finerprocessing of the semiconductor apparatus is facilitated, the samevoltage resistance as that of the conventional semiconductor apparatuscan be maintained.

Advantageous Effects of Invention

According to the manufacturing method of the semiconductor apparatus andthe semiconductor apparatus according to the various aspects of thepresent invention, an effect is achieved that its manufacturing cost canbe reduced and its unevenness generated during its manufacture can bereduced. Another effect is achieved that finer processing of thesemiconductor apparatus can be facilitated.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional diagram of an active portion of asemiconductor apparatus according to a first embodiment.

FIG. 2 is a diagram for explaining a manufacturing method of thesemiconductor apparatus according to the first embodiment.

FIG. 3 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the first embodiment.

FIG. 4 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the first embodiment.

FIG. 5 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the first embodiment.

FIG. 6 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the first embodiment.

FIG. 7 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the first embodiment.

FIG. 8 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the first embodiment.

FIG. 9 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the first embodiment.

FIG. 10 is a diagram for explaining current paths of the semiconductorapparatus according to the first embodiment.

FIG. 11 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to a second embodiment.

FIG. 12 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the second embodiment.

FIG. 13 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the second embodiment.

FIG. 14 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to a third embodiment.

FIG. 15 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the third embodiment.

FIG. 16 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the third embodiment.

FIG. 17 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the third embodiment.

FIG. 18 is a cross-sectional diagram of an active portion of thesemiconductor apparatus according to a fourth embodiment.

FIG. 19 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the fourth embodiment.

FIG. 20 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the fourth embodiment.

FIG. 21 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the fourth embodiment.

FIG. 22 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the fourth embodiment.

FIG. 23 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the fourth embodiment.

FIG. 24 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the fourth embodiment.

FIG. 25 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the fourth embodiment.

FIG. 26 is a cross-sectional diagram of an active portion of thesemiconductor apparatus according to a fifth embodiment.

FIG. 27 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the fifth embodiment.

FIG. 28 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the fifth embodiment.

FIG. 29 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the fifth embodiment.

FIG. 30 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the fifth embodiment.

FIG. 31 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the fifth embodiment.

FIG. 32 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the fifth embodiment.

FIG. 33 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to a sixth embodiment.

FIG. 34 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the sixth embodiment.

FIG. 35 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the sixth embodiment.

FIG. 36 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the sixth embodiment.

FIG. 37 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the sixth embodiment.

FIG. 38 is a cross-sectional diagram of a gate contact of thesemiconductor apparatus according to the sixth embodiment.

FIG. 39 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to a seventh embodiment.

FIG. 40 is a plan view of a planar structure of the semiconductorapparatus according to an eighth embodiment.

FIG. 41 is a cross-sectional diagram taken along a cutting line BB′ ofFIG. 40.

FIG. 42 is a cross-sectional diagram taken along a cutting line YY′ ofFIG. 40.

FIG. 43 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the eighth embodiment.

FIG. 44 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the eighth embodiment.

FIG. 45 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the eighth embodiment.

FIG. 46 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the eighth embodiment.

FIG. 47 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the eighth embodiment.

FIG. 48 is a plan view of the planar structure of the semiconductorapparatus according to a ninth embodiment.

FIG. 49 is a cross-sectional diagram taken along a cutting line Y2Y2′ ofFIG. 48.

FIG. 50 is a plan view of the planar structure of the semiconductorapparatus according a tenth embodiment.

FIG. 51 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to an eleventh embodiment.

FIG. 52 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the eleventh embodiment.

FIG. 53 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the eleventh embodiment.

FIG. 54 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the eleventh embodiment.

FIG. 55 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the eleventh embodiment.

FIG. 56 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the eleventh embodiment.

FIG. 57 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the eleventh embodiment.

FIG. 58 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the eleventh embodiment.

FIG. 59 is a diagram for explaining the manufacturing method of thesemiconductor apparatus according to the eleventh embodiment.

FIG. 60 is a cross-sectional diagram of a voltage-resistant structureportion of the semiconductor apparatus according to a twelfthembodiment.

FIG. 61 is a diagram for explaining the manufacturing method of theguard rings of the semiconductor apparatus according to the twelfthembodiment.

FIG. 62 is a diagram for explaining the manufacturing method of theguard rings of the semiconductor apparatus according to the twelfthembodiment.

FIG. 63 is a diagram for explaining the manufacturing method of theguard rings of the semiconductor apparatus according to the twelfthembodiment.

FIG. 64 is a diagram for explaining the manufacturing method of theguard rings of the semiconductor apparatus according to the twelfthembodiment.

FIG. 65 is a diagram for explaining the manufacturing method of theguard rings of the semiconductor apparatus according to the twelfthembodiment.

FIG. 66 is a diagram for explaining the manufacturing method of theguard rings of the semiconductor apparatus according to the twelfthembodiment.

FIG. 67 is a diagram for explaining the manufacturing method of theguard rings of the semiconductor apparatus according to the twelfthembodiment.

FIG. 68 is a diagram for explaining the manufacturing method of theguard rings of the semiconductor apparatus according to the twelfthembodiment.

FIG. 69 is a diagram for explaining the manufacturing method of theguard rings of the semiconductor apparatus according to the twelfthembodiment.

FIG. 70 is a cross-sectional diagram of the voltage-resistant structureportion of the semiconductor apparatus according to a thirteenthembodiment.

FIG. 71 is a diagram for explaining a cross-sectional structure of theactive portion vicinity of the voltage-resistant structure portiondepicted in FIG. 70.

FIG. 72 is a diagram for explaining the manufacturing method of thevoltage-resistant structure portion of the semiconductor apparatusaccording to the thirteenth embodiment.

FIG. 73 is a diagram for explaining the manufacturing method of thevoltage-resistant structure portion of the semiconductor apparatusaccording to the thirteenth embodiment.

FIG. 74 is a diagram for explaining the manufacturing method of thevoltage-resistant structure portion of the semiconductor apparatusaccording to the thirteenth embodiment.

FIG. 75 is a diagram for explaining the manufacturing method of thevoltage-resistant structure portion of the semiconductor apparatusaccording to the thirteenth embodiment.

FIG. 76 is a diagram for explaining the manufacturing method of thevoltage-resistant structure portion of the semiconductor apparatusaccording to the thirteenth embodiment.

FIG. 77 is a diagram for explaining the manufacturing method of thevoltage-resistant structure portion of the semiconductor apparatusaccording to the thirteenth embodiment.

FIG. 78 is a diagram for explaining the manufacturing method of thevoltage-resistant structure portion of the semiconductor apparatusaccording to the thirteenth embodiment.

FIG. 79 is a diagram for explaining the manufacturing method of thevoltage-resistant structure portion of the semiconductor apparatusaccording to the thirteenth embodiment.

FIG. 80 is a diagram for explaining the manufacturing method of thevoltage-resistant structure portion of the semiconductor apparatusaccording to the thirteenth embodiment.

FIG. 81 is a diagram for explaining the manufacturing method of thevoltage-resistant structure portion of the semiconductor apparatusaccording to the thirteenth embodiment.

FIG. 82 is a diagram for explaining the manufacturing method of thevoltage-resistant structure portion of the semiconductor apparatusaccording to the thirteenth embodiment.

FIG. 83 is a diagram for explaining the manufacturing method of thevoltage-resistant structure portion of the semiconductor apparatusaccording to the thirteenth embodiment.

FIG. 84 is a cross-sectional diagram of an equi-potential linedistribution generated in the semiconductor apparatus depicted in FIG.71.

FIG. 85 is a cross-sectional diagram of a voltage-resistant structureportion of the semiconductor apparatus according to a fourteenthembodiment.

FIG. 86 is a diagram for explaining a cross-sectional structure of theactive portion vicinity of the voltage-resistant structure portiondepicted in FIG. 85.

FIG. 87 is a diagram for explaining the manufacturing method of thevoltage-resistant structure portion of the semiconductor apparatusaccording to the fourteenth embodiment.

FIG. 88 is a diagram for explaining the manufacturing method of thevoltage-resistant structure portion of the semiconductor apparatusaccording to the fourteenth embodiment.

FIG. 89 is a diagram for explaining the manufacturing method of thevoltage-resistant structure portion of the semiconductor apparatusaccording to the fourteenth embodiment.

FIG. 90 is a diagram for explaining the manufacturing method of thevoltage-resistant structure portion of the semiconductor apparatusaccording to the fourteenth embodiment.

FIG. 91 is a cross-sectional diagram of an equi-potential linedistribution generated in the semiconductor apparatus depicted in FIG.86.

FIG. 92 is a cross-sectional diagram of an active portion of aconventional planar n-channel MOSFET.

FIG. 93 is a diagram for explaining the manufacturing processes of theconventional planar n-channel MOSFET.

FIG. 94 is a diagram for explaining the manufacturing processes of theconventional planar n-channel MOSFET.

FIG. 95 is a diagram for explaining the manufacturing processes of theconventional planar n-channel MOSFET.

FIG. 96 is a diagram for explaining the manufacturing processes of theconventional planar n-channel MOSFET.

FIG. 97 is a diagram for explaining the manufacturing processes of theconventional planar n-channel MOSFET.

FIG. 98 is a diagram for explaining the manufacturing processes of theconventional planar n-channel MOSFET.

FIG. 99 is a diagram for explaining the manufacturing processes of theconventional planar n-channel MOSFET.

FIG. 100 is a diagram for explaining a cross-sectional structure of thevoltage-resistant structure portion of the conventional planar n-channelMOSFET.

FIG. 101 is a diagram for explaining in detail a cross-sectionalstructure of active portion vicinity of a voltage-resistant structureportion of the conventional planar n-channel MOSFET.

FIG. 102 is a diagram for explaining the manufacturing processes of aguard ring of the conventional planar n-channel MOSFET.

FIG. 103 is a diagram for explaining the manufacturing processes of aguard ring of the conventional planar n-channel MOSFET.

FIG. 104 is a diagram for explaining the manufacturing processes of aguard ring of the conventional planar n-channel MOSFET.

FIG. 105 is a diagram for explaining the manufacturing processes of aguard ring of the conventional planar n-channel MOSFET.

FIG. 106 is a diagram for explaining the manufacturing processes of aguard ring of the conventional planar n-channel MOSFET.

FIG. 107 is a diagram for explaining the manufacturing processes of aguard ring of the conventional planar n-channel MOSFET.

FIG. 108 is a diagram for explaining the manufacturing processes of aguard ring of the conventional planar n-channel MOSFET.

FIG. 109 is a diagram for explaining the manufacturing processes of aguard ring of the conventional planar n-channel MOSFET.

FIG. 110 is a diagram for explaining the manufacturing processes of aguard ring of the conventional planar n-channel MOSFET.

DESCRIPTION OF EMBODIMENTS

Preferred embodiments of a manufacturing method of a semiconductorapparatus and a semiconductor apparatus according to the presentinvention will be described in detail with reference to the accompanyingdrawings. In the embodiments below, although “n” is defined as a firstconductivity and “p” is defined as a second conductivity, thedefinitions may be reversed. In the accompanying drawings, a constituentelement common in multiple drawings will be denoted by the samereference numeral in each of the drawings, and overlapping descriptionwill be omitted.

First Embodiment

FIG. 1 is a cross-sectional diagram of an active portion of asemiconductor apparatus according to a first embodiment. As depicted inFIG. 1, in the active portion 100 of the semiconductor apparatusaccording to the first embodiment, an n⁻ drift layer (firstsemiconductor region) 2 is disposed on an anterior side of an n-typelow-resistance layer 1. A semiconductor substrate having the n⁻ driftlayer 2 formed on the anterior side of the n-type low-resistance layer 1will be referred to as “semiconductor substrate”. An n counter layer 7is provided in a surface layer of the n⁻ drift layer 2. P⁻ well regions(second semiconductor regions) 10 are selectively provided such that thep⁻ well regions 10 each extends from the surface layer of the n counterlayer 7 and reaches the n⁻ drift layer 2. N source regions (thirdsemiconductor regions) 11 are selectively provided in the surface layerof the p⁻ well regions 10. P-type high-concentration regions 13 areprovided between the n source regions 11 in the surface layer of the p⁻well regions 10, and a portion of each p-type high concentration regions13 contacts the lower side of each of the n source regions 11.

A gate electrode (control electrode) 9 is disposed on a regionsandwiched by the n source regions 11 and the n counter layer 7 of thep⁻ well region 10 through a first insulating film 3 or 3 a. In whatfollows, this first insulating film will sometimes be called a gateinsulating film and identified using reference number 3 a (as in FIG.1), while at other times it will be called a screen oxide film andidentified using reference number 3 (as in FIG. 2). That is, referencenumbers 3 and 3 a are used in this disclosure to identify the sameinsulating film. An inter-layer insulating film (second insulating film)12 is disposed to cover the gate electrode 9. A source electrode (firstelectrode) 14 is disposed on the insulating film 12 (the secondinsulating film), and contacts the n source regions 11 and the p-typehigh-concentration regions 13 through openings of the insulating films12. The source electrode 14 is electrically connected to the n sourceregions 11. A protective film 15 is disposed on the source electrode 14.A drain electrode (second electrode) 16 is disposed on the posteriorside of the n-type low-resistance layer 1.

A manufacturing method of the semiconductor apparatus according to thefirst embodiment will be described. FIGS. 2 to 9 are diagrams forsequentially explaining the manufacturing method of the semiconductorapparatus according to the first embodiment. In the first embodiment, amethod of manufacturing a semiconductor apparatus whose guaranteedvoltage resistance is, for example, about 600 V will be described.

As depicted in FIG. 2, the n⁻ drift layer 2 whose thickness is, forexample, about 50 to 60 micrometers is grown on the anterior side of then-type low-resistance layer 1 by epitaxial growth whose surfaceconcentration is, for example, between 1*10¹⁴ and approximately 5*10¹⁴.The semiconductor substrate having the n⁻ drift layer 2 grown on then-type low-resistance layer 1 will be referred to as “semiconductorsubstrate”. A screen oxide film 3 (serving as the gate insulating film 3a of FIG. 1) is grown to have a thickness of, for example, severalhundred angstroms on the n⁻ drift layer 2. A nitride (SiN) film 4 isgrown to have a thickness of, for example, about 5000 angstrom on thescreen oxide film 3. In this case, the thickness of the nitride film 4merely has to be a thickness of which ions implanted by ion implantationdescribed later do not penetrate the nitride film 4, and be aboutseveral thousand angstroms.

As depicted in FIG. 3, the nitride film 4 is etched by photo-etchingusing a first mask not depicted and formed by pattern-forming with aresist film and thereby, nitride shielding films 61 are formed. In thiscase, the width of the nitride shielding film 61 is designed to be awidth by which p⁻ well regions described later are connected to eachother by horizontal diffusion.

As depicted in FIG. 4, n-type impurity ions at a higher concentrationthan that of the n⁻ drift layer 2 are implanted through the nitrideshielding films 61 from the anterior side of the semiconductor substrateand are thermally diffused. Thereby, an n counter layer 7 is formed. Atthis time, because the nitride shielding films 61 are formed on thesurface of the semiconductor substrate, the concentration of the ncounter layer 7 immediately beneath the nitride shielding films 61 islower than that of each of other regions. Therefore, when the p⁻ wellregions described later are formed, reduction of the p concentration dueto diffusion of p-type impurities can be suppressed. Thereby, JFETresistance of the p⁻ well regions can be reduced.

Although formation of the n counter layer 7 may be omitted, if the ncounter layer 7 is omitted, the distances between the p⁻ well regionsneed to be extended to reduce the JFET resistance of the p⁻ wellregions, which increases the size of each cell and reduces the densityof the cells, whereby the performance of the device is degraded.Consequently, it can be seen that the performance of the device isimproved by the formation of the n counter layer 7.

As depicted in FIG. 5, a poly-silicon layer 8 is grown on the gateinsulating film 3 a (SiO₂). During the growth of the poly-silicon layer8 or after the growth of the poly-silicon layer 8, the poly-siliconlayer 8 is caused to become the n type by doping an n-type impurity suchas phosphorus into the poly-silicon layer 8.

As depicted in FIG. 6, the gate electrode 9 is formed by selectivelyetching the poly-silicon using a second mask not depicted and formed bypattern-forming with a resist film. At this time, the gate electrodes 9and the nitride shielding films 61 are left on the anterior side of thesemiconductor substrate, that is, on the gate insulating film 3 a.

As depicted in FIG. 7, p-type impurity ions are implanted from theanterior side of the semiconductor substrate using the gate electrodes 9and the nitride shielding films 61 as a mask and thereby, the p⁻ wellregions 10 are formed having a depth of, for example, about 3micrometers. At this time, the p⁻ well regions 10 are caused to be alsoformed immediately beneath the nitride shielding films 61 by forming thep⁻ well regions 10 to be relatively deep.

N-type impurity ions are implanted from the anterior side of thesemiconductor substrate using the gate electrodes 9 and the nitrideshielding films 61 as a mask and thereby, n source regions 11 areformed, each having a depth of, for example, about 0.2 micrometers. Atthis time, no n source regions 11 are caused to be formed immediatelybeneath the nitride shielding films 61 by forming the n source regions11 to be relatively shallow.

As depicted in FIG. 8, an insulating film 12 is formed on the anteriorside of the semiconductor substrate. The insulating film 12 isselectively etched and the nitride shielding films 61 are simultaneouslyremoved, using a third mask not depicted and formed by patter-formingwith a resist film. At this time, the insulating film 12 is removed suchthat the insulating films 12 cover the gate electrodes 9 and regionsthat are sandwiched by the n source regions 11 of the p⁻ well regions 10and a portion of each of the n source regions 11 are exposed.

As depicted in FIG. 9, using the insulating films 12 as a mask, forexample, boron ions are implanted at an accelerating voltage high enoughfor the boron ions to penetrate the n source regions 11 and with about1*10²⁰/cm², and an annealing process is applied to the extent that theboron ions do not diffuse to the regions immediately beneath the gateelectrodes 9 and thereby, p-type high-concentration regions 13 areformed. With the annealing process, the p⁻ well regions 10 and the nsource regions 11 that are already ion-implanted are formed. At thistime, to thicken the p concentration of a portion of each of the p-typehigh concentration regions 13 on its side close to the gate electrode 9,that is, regions immediately beneath the n source regions 11, obliqueion implantation may be executed. However, in this case, the processesare increased by the processes necessary for the oblique ionimplantation. By forming the p-type high-concentration regions 13 inthis manner, latching-up can be prevented.

As depicted in FIG. 1, Al—Si is deposited on the anterior side of thesemiconductor substrate and Al—Si separation is executed in regions notdepicted and thereby, a source electrode 14 is formed. A protective film15 is formed on the source electrode 14. A drain electrode 16 is formedon the posterior side of the semiconductor substrate. As described, thesemiconductor apparatus according to the first embodiment is completed.

Current paths of the semiconductor apparatus according to the firstembodiment will be described with reference to FIG. 10. FIG. 10 is adiagram for explaining the current paths of the semiconductor apparatusaccording to the first embodiment. As depicted in FIG. 10, a terminal isconnected to each of the gate electrodes 9, the source electrode 14, andthe drain electrode 16, and a positive voltage at a specific value orhigher is applied to the gate electrode 9. Thereby, regions under thegate electrodes 9 on the top surface of the p⁻ well regions 10 areinverted to n layers and thereby, the drain electrode 16 and the sourceelectrode 14 are connected to each other by n-type semiconductors.Therefore, this path becomes conductive according to the polarity of thevoltage applied between the drain and the source. More specifically, forexample, when the gate and the source are short-circuited and the draincurrent value is 1 mA, the voltage between the drain and the source is660 V and “Ron*A” that is the product of an on-resistance value “Ron”and an area value “A” is 8 Ohm*mm². For example, a voltage of 10 V isapplied to the gate electrodes 9 and the drain current value is 1 mA,the threshold voltage is about 3.0 V.

According to the first embodiment, the semiconductor apparatus havingthe same performance as that of the conventional semiconductor apparatuscan be manufactured even when the number of masks used during itsmanufacturing processes is even reduced by one. One process of forming aresist film and pattern-forming with it is omitted and therefore, themanufacturing cost is reduced. Because the number of masks is reduced,the alignment for the device is improved relative to the conventionalalignment and the variation among devices caused during theirmanufacture can be reduced. After forming the gate electrodes, only oneheat treatment session is applied. Therefore, production of bird's beakscan be prevented.

Second Embodiment

A manufacturing method of a semiconductor apparatus according to asecond embodiment will be described. FIGS. 11 to 13 are diagrams forsequentially explaining the manufacturing method of the semiconductorapparatus according to the second embodiment. In the manufacturingmethod of the semiconductor apparatus according to the secondembodiment, a CVD (Chemical Vapor Deposition) shielding film formed byCVD is used as a mask instead of the nitride shielding film.

As depicted in FIG. 11, a CVD film 42 formed by CVD is grown to have athickness of, for example, about 5,000 angstrom on the n⁻ drift layer 2.In this case, the thickness of the CVD film 42 merely has to be athickness for ions by ion implantation described later not to penetratethe CVD film 42, and may be about several thousand angstroms.

As depicted in FIG. 12, the CVD film 42 is etched by photo-etching usinga first mask not depicted and formed by pattern-forming with a resistfilm and thereby, CVD shielding films 62 are formed.

As depicted in FIG. 13, the screen oxide film 3 is formed on the n⁻drift layer 2. After forming the screen oxide film 3, the n counterlayer 7 is formed by executing the same processes as those of the firstembodiment. The processes to be executed thereafter are same as those ofthe first embodiment and will not again be described. Therefore, the twomasks are used in those processes executed thereafter and three masks intotal including the first mask are used for completing the semiconductorapparatus.

According to the second embodiment, the same effects as those of thefirst embodiment can be obtained.

Third Embodiment

A manufacturing method of a semiconductor apparatus according to a thirdsemiconductor will be described. FIGS. 14 to 17 are diagrams forsequentially explaining the manufacturing method of the semiconductorapparatus according to the third embodiment. In the manufacturing methodof the semiconductor apparatus according to the third embodiment, aLOCOS oxide film is used as a mask instead of the nitride shielding filmor the CVD shielding film.

As depicted in FIG. 14, the screen oxide film 3 is grown to have athickness of, for example, about several hundred angstroms on the n⁻drift layer 2. A nitride film 43 is grown to have a thickness of, forexample, about several thousand angstroms on the screen oxide film 3.

As depicted in FIG. 15, the nitride film 43 is etched by photo-etchingusing the first mask not depicted and formed by pattern-forming with aresist film and thereby, openings 5 are formed.

As depicted in FIG. 16, LOCOS oxide films 63 are formed in the openings5. The thickness of the LOCOS oxide films 63 merely has to be athickness of which ions by ion implantation described later do notpenetrate the LOCOS oxide films 63, and is, for example, about severalthousand angstroms.

As depicted in FIG. 17, the nitride film 43 is removed, n-type impurityions at a concentration higher than that of the n⁻ drift layer 2 areimplanted from the anterior side of the semiconductor substrate throughthe LOCOS oxide films 63, and are thermally diffused. Thereby, the ncounter layer 7 is formed. The processes to be executed thereafter aresame as those in the first or the second embodiment and will not againbe described. Therefore, the two masks are used in the processes to beexecuted thereafter and three masks in total including the first maskare used for completing the semiconductor apparatus. The LOCOS oxidefilms 63 are formed before the n source regions are formed andtherefore, the top surface of the n source regions are not oxidized.Therefore, increase of the resistance due to oxidation can be prevented.

According to the third embodiment, the same effects as those of thefirst or the second embodiment can be obtained.

Fourth Embodiment

A semiconductor apparatus according to a fourth embodiment will bedescribed. FIG. 18 is a cross-sectional diagram of an active portion ofthe semiconductor apparatus according to the fourth embodiment. In theactive portion of the semiconductor apparatus according to the fourthembodiment, a LOCOS oxide film 64 covered by the gate electrode 9 isprovided. The LOCOS oxide film 64 is provided in a region that issandwiched by the p⁻ well regions 10 of the n⁻ drift layer 2.

A manufacturing method of the semiconductor apparatus according to thefourth embodiment will be described. FIGS. 19 to 25 are diagrams forsequentially explaining the manufacturing method of the semiconductorapparatus according to the fourth embodiment.

As depicted in FIG. 14, the screen oxide film 3 is grown to have athickness of, for example, about several hundred angstroms on the n⁻drift layer 2. The nitride film 43 is grown to have a thickness of, forexample, about several thousand angstroms on the screen oxide film 3.

As depicted in FIG. 19, the nitride film 43 is etched by photo-etchingusing the first mask not depicted and formed by pattern-forming with aresist film and thereby, the openings 5 (first openings) are formed, andopenings (second openings) 51 are formed in the regions to be laterformed with the gate electrodes. The second openings 51 are each formedto have a length with which ends of the p⁻ well regions 10 describedlater do not reach each other.

As depicted in FIG. 20, the LOCOS oxide films 63 are formed in the firstopenings 5 and the LOCOS oxide films 64 are formed in the secondopenings 51. The thickness of each of the LOCOS films 63 and 64 merelyhas to be a thickness of which ions implanted by ion implantationdescribed later do not penetrate the LOCOS oxide films 63 and 64 and is,for example, about several thousand angstroms. The nitride film 43 isremoved.

As depicted in FIG. 21, n-type impurity ions at a concentration higherthan that of the n⁻ drift layer 2 are implanted from the anterior sideof the semiconductor substrate through the LOCOS oxide films 63 and 64,and are thermally diffused. Thereby, the n counter layer 7 is formed.The screen oxide film 3 is removed.

As depicted in FIG. 22, the gate insulating film 3 a is grown to be, forexample, about several hundred angstroms thick on the anterior side ofthe semiconductor substrate. The poly-silicon 8 is grown on the gateinsulating film 3 a. Thereby, the LOCOS oxide films 63 and 64 arecovered by the poly-silicon 8. During the growth of the poly-silicon 8or after the growth of the poly-silicon 8, the poly-silicon 8 is causedto become the n type by doping an n-type impurity such as phosphorusthereinto.

As depicted in FIG. 23, the gate electrodes 9 are formed by selectivelyetching the poly-silicon 8 using the second mask not depicted and formedby pattern-forming with a resist film. At this time, the poly-silicon 8is etched such that the LOCOS oxide films 64 are covered by the gateelectrodes 9. The LOCOS oxide films 64 are left between the gateelectrodes 9 and the n⁻ drift layer 2. Thereby, the gate electrodes 9covering the LOCOS oxide films 64, and the LOCOS oxide films 63 aredisposed on the anterior side of the semiconductor substrate, that is,on the gate insulating film 3 a.

As depicted in FIG. 24, p-type impurity ions are implanted from theanterior side of the semiconductor substrate using the gate electrodes 9and the LOCOS oxide films 63 as a mask. Thereby, the p⁻ well regions 10are formed, each having a depth of, for example, about 3 micrometers. Atthis time, by forming the p⁻ well regions 10 to be relatively deep, thep⁻ well regions 10 are caused to be also formed immediately beneath theLOCOS oxide films 63.

N-type impurity ions are implanted from the anterior side of thesemiconductor substrate using the gate electrodes 9 and the nitrideshielding film 61 as a mask and thereby, the n source regions 11 eachhaving a depth of, for example, about 0.2 micrometers are formed. Atthis time, by forming the n source regions 11 to be relatively shallow,the n source regions 11 are caused not to be formed immediately beneaththe LOCOS oxide films 63.

As depicted in FIG. 25, the insulating film 12 is formed on the anteriorside of the semiconductor substrate. The insulating film 12 isselectively removed using the third mask not depicted and formed bypattern-forming with a resist film and simultaneously, the LOCOS oxidefilms 63 are removed. At this time, the insulating film 12 is removedsuch that the insulating film 12 covers the gate electrodes 9 and theregions that are sandwiched by the n source regions 11 of the p⁻ wellregions 10, and a portion of each of the n source regions 11 areexposed. The LOCOS oxide films 64 are covered by the gate electrodes 9and therefore, are not removed and are left. The processes to beexecuted thereafter are same as those of the first to the thirdembodiments and will not again be described. Therefore, the one mask isused in the processes to be executed thereafter and three masks arenecessary for forming the semiconductor apparatus according to thefourth embodiment similarly to the first to the third embodiments.

According to the fourth embodiment, the same effects as those of thefirst to the third embodiments can be obtained. The oxide films thateach are partially thicker than the ordinary gate insulating films canbe formed immediately beneath the gate electrodes without increasing thenumber of masks used during the manufacturing processes. Therefore, thecapacity between the gate and the drain and the capacity between thegate and the source can significantly be reduced relative to those ofthe first to the third embodiments without increasing the manufacturingcost.

Fifth Embodiment

A semiconductor apparatus according to a fifth embodiment will bedescribed. FIG. 26 is a cross-sectional diagram of an active portion ofthe semiconductor apparatus according to the fifth embodiment. In theactive portion of the semiconductor apparatus according to the fifthembodiment, a LOCOS oxide film 65 that is covered by the gate electrode9 is provided. The LOCOS oxide film 65 is provided in a region that issandwiched by the p⁻ well regions 10 of the n⁻ drift layer 2 such that aportion of the LOCOS oxide film 65 contacts the p⁻ well regions 10.

A manufacturing method of the semiconductor apparatus according to thefifth embodiment will be described. FIGS. 27 to 32 are diagrams forsequentially explaining the manufacturing method of the semiconductorapparatus according to the fifth embodiment. In the fifth embodiment, asdepicted in FIG. 14, the screen oxide film 3 is grown to have athickness of, for example, about several hundred angstroms on the n⁻drift layer 2. The nitride film 43 is grown to have a thickness of, forexample, about several thousand angstroms on the screen oxide film 3.

As depicted in FIG. 27, the nitride film 43 is etched by photo-etchingusing the first mask not depicted and formed by pattern-forming with aresist film and thereby, the openings (first openings) 5 are formed and,in the regions to have the gate electrodes later formed therein,openings (second openings) 52 are formed such that a portion of each ofthe openings 52 contacts the p⁻ well region formed later.

As depicted in FIG. 28, the LOCOS oxide films 63 are formed in the firstopenings 5 and the LOCOS oxide films 65 are formed in the secondopenings 52. The thickness of the LOCOS oxide films 63 and 65 merely hasto be a thickness of which ions implanted by ion implantation describedlater do not penetrate the LOCOS oxide films 63 and 65 and is, forexample, about several thousand angstroms. The nitride film 43 isremoved.

As depicted in FIG. 29, n-type impurity ions at a concentration higherthan that of the n drift layer 2 are implanted from the anterior side ofthe semiconductor substrate through the LOCOS oxide films 63 and 65, andare thermally diffused. Thereby, the n counter layer 7 is formed. Thescreen oxide film 3 is removed.

As depicted in FIG. 30, the gate insulating film 3 a is grown to have athickness of, for example, about several hundred angstroms on theanterior side of the semiconductor substrate. The poly-silicon 8 isgrown on the gate insulating film 3 a. Thereby, the LOCOS oxide films 63and 65 are covered by the poly-silicon 8. During the growth of thepoly-silicon 8 or after the growth of the poly-silicon 8, thepoly-silicon 8 is caused to become the n type by doping an n-typeimpurity such as phosphorus thereinto. If the width and the position ofthe LOCOS oxide film 65 are accommodated within the p well region 10,the same property is obtained.

As depicted in FIG. 31, the poly-silicon is selectively etched using thesecond mask not depicted and formed by pattern-forming with a resistfilm and thereby, the gate electrodes 9 are formed. At this time, thepoly-silicon is etched such that the LOCOS oxide films 65 are covered bythe gate electrodes 9. The LOCOS oxide films 65 are left between thegate electrodes 9 and the n⁻ drift layer 9. Thereby, the gate electrodes9 covering the LOCOS oxide films 65, and the LOCOS oxide films 63 aredisposed on the anterior side of the semiconductor substrate, that is,on the gate oxide film 3 a.

As depicted in FIG. 32, p-type impurity ions are implanted from theanterior side of the semiconductor substrate using the gate electrodes 9and the LOCOS oxide films 63 as a mask and thereby, the p⁻ well regions10 are formed, each having a depth of, for example, about 3 micrometers.At this time, the p⁻ well regions 10 are caused to be formed immediatelybeneath the LOCOS oxide films 63 by forming the p⁻ well regions 10 to berelatively deep. The portion of each of the p⁻ well regions 10 contactsthe LOCOS oxide film 65.

N-type impurity ions are implanted from the anterior side of thesemiconductor substrate using the gate electrodes 9 and the nitrideshielding film 61 as a mask and thereby, the n source regions 11 areformed, each having a depth of, for example, about 0.2 micrometers. Atthis time, no n source region 11 is caused to be formed immediatelybeneath the LOCOS oxide films 63 by forming the n source regions 11 tobe relatively shallow. The processes to be executed thereafter are sameas those in the first to the fourth embodiments and will not again bedescribed. Therefore, the one mask is used in the processes to beexecuted thereafter and three masks are necessary for forming thesemiconductor apparatus according to the fifth embodiment similarly tothe first to the fourth embodiments.

In the fourth and the fifth embodiments, the method of forming the LOCOSoxide films formed by thermal oxidation, immediately beneath the gateelectrodes has been described. However, the oxide films are not limitedto the above. More specifically, as described in, for example, thesecond embodiment, oxide films formed by CVD (CVD shielding films) maybe formed immediately beneath the gate electrodes.

According to the fifth embodiment, the same effects as those in thefirst to the fourth embodiments can be obtained. The capacity betweenthe gate and the source can also be reduced. According to the fifthembodiment, no current flows in the region that contacts the LOCOS oxidefilm 65 in the gate electrode 9 because the gate can not be turned on.Therefore, the variation of the current to the variation of the gatevoltage can be made more insensitive than that of the first to thefourth embodiments without increasing the number of masks used duringthe manufacturing processes. The current paths between the source andthe drain can easily be reduced. In this case, for a vertical MOSFET forabout 600 V, most of the resistant portions that account for in thecurrent paths is determined by the impurity concentration of the crystaland therefore, the resistance of the device is almost not increased evenwhen the LOCOS oxide film 65 is present in the gate electrode 9.

Sixth Embodiment

A manufacturing method of a semiconductor apparatus according to a sixthembodiment will be described. In the sixth embodiment, the gateelectrode is used as a mask instead of the nitride shielding film, theCVD shielding film, or the LOCOS oxide film. FIGS. 33 to 37 are diagramsfor sequentially explaining the manufacturing method of thesemiconductor apparatus according to the sixth embodiment. As depictedin FIG. 33, the gate insulating film 3 a is formed on the anterior sideof the semiconductor substrate. The poly-silicon 8 is formed on the gateinsulating film 3 a. Before forming the poly-silicon 8, the n counterlayer 7 may be formed by implanting n-type impurity ions at aconcentration higher than that of the n⁻ drift layer 2 and thermallydiffusing the ions.

As depicted in FIG. 34, the poly-silicon is etched using the first maskformed by pattern-forming with a resist film. At this time, thepoly-silicon in the regions to execute the function as a shielding filmis not etched and left in addition to that in the regions to execute thefunction as the gate electrode 9. The gate electrode that executes thefunction as the shielding film is referred to as “gate shielding film91”.

As depicted in FIG. 35, the ion implantation is executed to form the p⁻well regions 10 and the source regions 11, using the gate electrodes 9and the gate shielding films 91 as a mask similarly to the first to thefifth embodiments.

As depicted in FIG. 36, the insulating film 12 is formed on the gateinsulating film 3 a, the gate electrodes 9, and the gate shielding films91. The insulating film 12 is selectively etched using a second mask 21formed by pattern-forming with a resist film. At this time, theinsulating film 12 is etched such that the gate electrodes 9 are coveredby the insulating film 12 and the gate shielding films 91 are exposed.

As depicted in FIG. 37, the second mask and the gate shielding films 91are removed. At this time, the gate electrodes 9 are covered by theinsulating film 12 and therefore, are not removed and are left. Forexample, boron ions are implanted at an accelerating voltage high enoughfor the ions to penetrate the n source regions 11 and an annealingprocess is applied to the extent that the boron ions do not diffuse tothe regions immediately beneath the gate electrodes 9 and thereby, thep-type high-concentration regions 13 are formed. The processes to beexecuted thereafter are same as those of the first to the fifthembodiments and will not again be described. Therefore, no mask is usedin the processes to be executed thereafter and two masks in total areused to complete the semiconductor apparatus in the sixth embodiment.

FIG. 38 is a cross-sectional diagram of a gate contact of thesemiconductor apparatus according to the sixth embodiment. As depictedin FIG. 38, for the gate contact 54 of the semiconductor apparatusaccording to the sixth embodiment, the gate electrodes 9 are etched andare not present. However, when a thick oxide film 3 b is formed beneaththe gate contact 54, the gate is not short-circuited and the gatecontact 54 can contact the gate electrode 9 using the cross-sectionformed by the etching and therefore, the pattern formation for theetching the contact does not need to be divided into two sessions.

According to the sixth embodiment, the same effects as those of thefirst to the fifth embodiments can be obtained. According to the sixthembodiment, the semiconductor apparatus having the same performance asthat of the conventional semiconductor apparatus can be manufacturedeven when the number of masks used during its manufacturing processes issmaller than that of the conventional semiconductor apparatus by two.Therefore, the manufacturing cost can be more reduced and the variationamong devices can be more reduced than those of the first to the fifthembodiments.

Seventh Embodiment

A manufacturing method of a semiconductor apparatus according to aseventh embodiment will be described. For the semiconductor apparatusaccording to the seventh embodiment, in the manufacturing method of thesemiconductor apparatus according to the sixth embodiment, the gateshielding film may not be completely exposed when the insulating film isremoved. FIG. 39 is a diagram for explaining the manufacturing method ofthe semiconductor apparatus according to the seventh embodiment. Asdepicted in FIG. 39, when the gate shielding film 91 is removed, aportion of the gate shielding film 91 may be left at each end of theinsulating films 12. Even when the portion of the gate shielding film 91is left, the property of the device is not varied.

According to the seventh embodiment, the same effects as those of thesixth embodiment can be obtained.

Eighth Embodiment

A semiconductor apparatus according to an eighth embodiment will bedescribed. FIG. 40 is a plan view of the planar structure of thesemiconductor apparatus according to the eighth embodiment. In FIG. 40,the planar structure is depicted omitting the source electrode and theprotective film to clarify the shapes of the n source regions 11 and thep-type high-concentration regions 13. FIG. 41 is a cross-sectionaldiagram taken along a cutting line BB′ of FIG. 40. FIG. 42 is across-sectional diagram taken along a cutting line YY′ of FIG. 40. Thecross-sectional structure taken along the cutting line AA′ of FIG. 40 isthe structure same as that of the semiconductor apparatus described inthe first to the seventh embodiments. In the eighth embodiment, thoughthe n⁻ drift layer and the n counter layer are not formed, the n⁻ driftlayer and the n counter layer may be formed similarly to the first tothe fifth embodiments.

In the semiconductor apparatus according to the eighth embodiment, eachof the regions having the p-type high-concentration region 13 exposedtherein is provided such that the planar shape thereof is a stripeshape. A region having no p-type high-concentration region 13 exposedtherein is provided in a portion of the stripe shape by the p-typehigh-concentration region 13. As depicted in FIG. 41 or 42, the regionhaving the n source region 11 exposed therein is formed in the portionof the surface layer of the p-type high-concentration region 13.

A manufacturing method of the semiconductor apparatus according to theeighth embodiment will be described. FIGS. 43 to 47 are diagrams forsequentially explaining the manufacturing method of the semiconductorapparatus according to the eighth embodiment. Similarly to the sixth orthe seventh embodiment, as depicted in FIG. 33, the gate insulating film3 a is formed on the anterior side of the semiconductor substrate andthe poly-silicon 8 is formed on the gate insulating film 3 a.

As depicted in FIG. 43, the poly-silicon is etched using the first maskthat is same as that used when the poly-silicon is etched in FIG. 34. Atthis time, different from the sixth or the seventh embodiment, only thegate electrodes 9 are formed and the gate shielding film is not formed.Though an example of using the gate shielding film as a mask isdescribed in the eighth embodiment, the mask is not limited to this. Asdescribed in the first to the fifth embodiments, the nitride shieldingfilm, the CVD shielding film, or the LOCOS oxide film may be used as amask. In this case, in a region having the cross-sectional structuretaken along the cutting line AA′ of FIG. 40, similarly to the first tothe fifth embodiments, a shielding film such as the nitride shieldingfilm, the CVD shielding film, or the LOCOS oxide film may be formed and,in a region having the cross-sectional structure taken along the cuttingline BB′, the above shielding film may not be formed.

For example, in the case where a shielding film whose planar shape is astripe is formed, when the nitride film or the CVD film is etched byphoto-etching (see FIGS. 3 and 12) or when the openings to form theLOCOS oxide films therein are formed (see FIGS. 15, 19, and 27), theetching is executed using a mask with which a portion of the shieldingfilm or the LOCOS oxide film whose planar shape is a stripe is removed.By doing this, as depicted in FIG. 43, when the poly-silicon is etchedand the gate electrodes 9 are formed, a region having no shielding filmor no LOCOS oxide film is formed between the gate electrodes 9.

As depicted in FIG. 44, similarly to the first to the seventhembodiments, when ions are implanted into the regions that become the nsource regions 11 after ions are implanted into the regions that becomethe p⁻ well regions 10, the n source regions 11 are formed on the entiresurface between the gate electrodes 9 of the p⁻ well regions 10 becauseno shielding film or no LOCOS oxide film is present between the gateelectrodes 9.

As depicted in FIG. 45, the insulating film 12 is formed and theinsulting film 12 is selectively etched using the second mask 21.Therefore, as depicted in FIG. 46, when the p-type high-concentrationregions 13 are formed using the insulating film 12 as a mask, p-typeimpurity ions are implanted at an accelerating voltage high enough forthe ions to penetrate the n source regions 11. Therefore, the p-typehigh-concentration regions 13 are formed beneath the n source regions11. The p-type high-concentration regions 13 are not exposed in thesurface of the semiconductor substrate.

As depicted in FIG. 47, the source electrode 14 is formed. As described,when the regions of the structure described in the first to the seventhembodiments are formed, a region having a different area for the sourceelectrode and the source region to contact each other therein from thatof the first to the seventh embodiments can simultaneously be formed.

According to the eighth embodiment, when the semiconductor apparatushaving the cross-sectional structure described in the first to theseventh embodiments is formed, the region having the p-typehigh-concentration region not reaching the source electrode cansimultaneously be formed without increasing the number of masks. Asdescribed, regions having different mutual conductance can be formedsimultaneously. By adjusting the regions having the p-typehigh-concentration region exposed therein and the regions having thep-type high-concentration region not exposed therein, the ratio of theregions having different mutual conductance can be varied and the mutualconductance can be reduced. Thereby, reduction of the amount ofavalanche resisted can be suppressed.

Ninth Embodiment

A semiconductor apparatus according to a ninth embodiment will bedescribed. FIG. 48 is a plan view of the planar structure of thesemiconductor apparatus according to the ninth embodiment. FIG. 49 is across-sectional diagram taken along a cutting line Y2Y2′ of FIG. 48. InFIG. 48, the planar structure is depicted omitting the source electrodeand the protective film to clarify the shapes of the n source regions 11and the p-type high-concentration regions 13.

In the ninth embodiment, as depicted in FIGS. 48 and 49, a plurality ofregions each having the n source region 11 exposed therein are presentfor each one line portion of a stripe formed by the p-typehigh-concentration region 13.

According to the ninth embodiment, the same effects as those of theeighth embodiment can be obtained.

Tenth Embodiment

A semiconductor apparatus according to a tenth embodiment will bedescribed. FIG. 50 is a plan view of the planar structure of thesemiconductor apparatus according the tenth embodiment. In FIG. 50, theplanar structure is depicted omitting the source electrode and theprotective film to clarify the shapes of the n source regions 11 and thep-type high-concentration regions 13. As depicted in FIG. 50, exposedregions of the n source regions 11 of the line portions respectively ofa stripped shape for by the p-type high-concentration regions 13 may bestaggered in position with exposed regions of the n source region 11 ofan adjacent line portion. In this case, the structure having the p-typehigh-concentration regions 13 that contact the source electrodedescribed in the first to the seventh embodiments, and the structurehaving only the n source regions 11 that contact the source electrodedescribed in the eighth embodiment, are formed adjacent to each other.

According to the tenth embodiment, the same effects as those of theeighth or the ninth embodiment can be obtained.

Eleventh Embodiment

A manufacturing method of a semiconductor apparatus according to aneleventh embodiment will be described. FIGS. 51 to 59 are diagrams forsequentially explaining the manufacturing method of the semiconductorapparatus according to the eleventh embodiment. As depicted in FIG. 51,the n⁻ drift layer 2 having a thickness of, for example, about 50 to 60micrometers is deposited on the anterior side of the n-typelow-resistance layer 1 by, for example, epitaxial growth whose surfaceconcentration is between 1*10¹⁴ and approximately 5*10¹⁴. Thesemiconductor substrate having the n drift layer 2 deposited on then-type low-resistance layer 1 is referred to as “semiconductorsubstrate”. A screen oxide film 3 is grown to have a thickness of, forexample, several hundred angstroms on the n⁻ drift layer 2. N-typeimpurity ions at the higher concentration than that of the n⁻ driftlayer 2 are implanted from the surface of the screen oxide film 3 andthereby, the n counter layer 7 is formed. A nitride film 44 is formed onthe screen oxide film 3.

As depicted in FIG. 52, the nitride film 44 is etched by photo-etchingusing the first mask not depicted and formed by pattern-forming with aresist film and thereby, openings 55 are formed in the nitride film 44through which the n⁻ drift layer 2 (n counter layer 7) is exposed.P-type impurity ions are implanted from the openings 55 into the surfacelayer of the n counter layer 7 and thereby, the p⁻ well regions 10 areformed.

As depicted in FIG. 53, p-type impurity ions at a concentration higherthan that of the p well regions 10 are implanted into the openings 55into which ions are implanted to form the p⁻ well regions 10 andthereby, the p-type high-concentration regions 13 are formed. Asdepicted in FIG. 54, locos oxide films 66 are formed on the p-typehigh-concentration regions 13 using the openings 55.

As depicted in FIG. 55, the nitride film 44 is removed and p⁻ regions 17are formed in the surface layer of the n⁻ drift layer 2 using the LOCOSoxide films 66. By forming the p regions 17 as described, for example,even when regions having the p⁻ well regions 10 and gate electrodesformed later that overlap with each other are each narrow, the p regions17 become channels and Vth can be adjusted. “Vth” is a gate thresholdvoltage at which a drain current starts to flow.

As depicted in FIG. 56, the gate insulating film 3 a is formed on the p⁻regions 17. The poly-silicon is formed on the gate insulating film 3 a.The gate insulating film 3 a and the poly-silicon are selectively etchedusing the second mask not depicted and formed by pattern-forming with aresist film and thereby, the gate electrodes 9 are formed. The n sourceregions 11 are formed by implanting n-type impurity ions using the gateelectrodes 9 and the LOCOS oxide films 66 as a mask.

As depicted in FIG. 57, the LOCOS oxide films 66 are removed. Theinsulating film 12 is formed on the anterior side of the semiconductorsubstrate and the insulating film 12 is selectively removed using thethird mask not depicted and formed by pattern-forming with a resistfilm. At this time, the removal is executed such that the p⁻ wellregions 10 and the n source regions 11 are exposed and the insulatingfilm 12 covers the gate electrodes 9.

As depicted in FIG. 58, an Al—Si film is deposited on the anterior sideof the semiconductor substrate and Al—Si film separation is executed ina region not depicted and thereby, the source electrode 14 is formed.The source electrode 14 commonly contacts the p-type high-concentrationregions 13 and the n source regions 11. The source electrode and thegate electrodes 9 are insulated from each other by the insulating film12.

As depicted in FIG. 59, the protective film 15 is formed on the sourceelectrode 14. The drain electrode 16 is formed on the posterior side ofthe semiconductor substrate. The semiconductor apparatus according tothe eleventh embodiment is completed as described. In the eleventhembodiment, the n counter layer 7 is formed in FIG. 51. However, theembodiment may be adapted to execute the processes to be executed afterthat of FIG. 52 without forming the n counter layer 7.

According to the eleventh embodiment, the same effects as those of thefirst to the fifth embodiments can be obtained.

Twelfth Embodiment

A voltage-resistant structure portion of a semiconductor apparatusaccording to a twelfth embodiment will be described. FIG. 60 is across-sectional diagram of the voltage-resistant structure portion ofthe semiconductor apparatus according to the twelfth embodiment. Asdepicted in FIG. 60, in the voltage-resistant structure portion 200 ofthe semiconductor apparatus according to the twelfth embodiment, a p⁻region 10 b is provided in the surface layer of the n⁻ drift layer 2, ona loop, connected to the p″ well regions 10, surrounding the p⁻ wellregions 10, and having the impurity concentration lower than that of andthe diffusion depth deeper than that of the p⁻ well regions 10. P guardrings 10 c are provided each in a loop, surrounding the p⁻ region 10 b,connected to the p⁻ region 10 b at its end, having the impurityconcentration equal to that of and the diffusion depth equal to that ofthe p⁻ region 10 b.

In FIG. 60, the four p guard rings 10 c are formed and overlappingpoints 23 becomes smaller toward the outer circumference (edgestructure) of the chip. The outermost p guard ring 10 c is providedapart from the p guard ring 10 c immediately beside it. By providing thep guard rings 10 c as described, peaks of the electric field at curvedportions of the p guard rings 10C are equalized.

A p stopper region 77 is provided in the surface layer of the n⁻ driftlayer 2 in the outermost circumference of the chip. A p contact region73 is provided in the surface layer of the p stopper region 77. The pcontact region 73 is connected to a metal film 78 through a contactopening 76 provided for the insulating films 18 and 19.

A manufacturing method of the guard rings of the semiconductor apparatusaccording to the twelfth embodiment will be described. FIGS. 61 to 69are diagrams for sequentially explaining the manufacturing method of theguard rings of the semiconductor apparatus according to the twelfthembodiment. In FIGS. 61 to 69, the description will be given assumingthat one guard ring that the voltage-resistant structure portion hasdoes not overlap with an adjacent guard ring.

As depicted in FIG. 61, similarly to the eleventh embodiment, the n⁻drift layer 2 having the thickness of, for example, about 50 to 60micrometers is deposited on the anterior side of the n-typelow-resistance layer 1 by, for example, epitaxial growth whose surfaceconcentration is between 1*10¹⁴ and approximately 5*10¹⁴. Thesemiconductor substrate having the n⁻ drift layer 2 deposited on then-type low-resistance layer 1 is referred to as “semiconductorsubstrate”. In the twelfth embodiment, an insulating oxide film 18 isformed on the n⁻ drift layer 2.

As depicted in FIG. 62, the insulating film 18 is selectively etchedusing a fifth mask formed by pattern-forming with a resist film andthereby, an opening 56 is formed.

As depicted in FIG. 62, when the n counter layer 7 is formed in theactive portion in FIG. 51, ion implantation is simultaneously executedinto the opening 56 and thereby, the n counter layer 7 is formed. Bydoing this, the n counter layer 7 is formed only in the opening 56. Whenthe nitride film 44 is formed in the active portion, a nitride film 45is simultaneously formed on the n⁻ drift layer 2 and the insulating film18.

As depicted in FIG. 63, when the nitride film 44 of the active portionis etched in FIG. 52, the nitride film 45 is etched by photo-etchingusing the same first mask and thereby, a plurality of openings 57 areformed in the nitride film 45 such that the n⁻ drift layer 2 (n counterlayer 7) is exposed in the openings 57. When the p⁻ well regions 10 areformed in the active portion, the p guard rings 10 c configured by theplurality of p⁻ well regions 10 connected to one after another areformed by implanting p-type impurity ions into the openings 57.

In the voltage-resistant structure portion, different from the activeportion, the n counter layer 7 is selectively provided. No n-typeimpurity ions are implanted into regions immediately beneath theinsulating film 18. Therefore, the low-concentration p⁻ well regions 10can be diffused in the horizontal direction from the active portion andbe expanded. Therefore, the impurity concentration of the p⁻ wellregions 10 can be made lower than that of the active portion and theregions between the p guard rings 10 c tend to be depleted. Therefore,the voltage resistance of these regions becomes higher than that of theactive portion. The openings 57 formed in the nitride film 45 are madenarrower than the openings in the active portion and thereby, the totalamount of the ions implanted into the voltage-resistant structureportion 200 can be made smaller than the total amount of the ionsimplanted into the active portion. Therefore, the impurity concentrationof the p⁻ well regions 10 is lower than that of the active portion andthe p⁻ well regions 10 tend to be depleted. Therefore, the voltageresistance of the p⁻ well regions 10 is higher than that of the activeportion. By doing this, when an avalanche current occurs, the currenttends to flow to the active portion and the avalanche amount resisted isimproved.

As depicted in FIG. 64, when the p-type high-concentration regions 13are formed in the active portion in FIG. 53, p-type impurity ions at aconcentration higher than that of the p guard rings 10 c aresimultaneously implanted into the openings 57 into which the ions areimplanted to form the p guard rings 10 c and thereby, the p-typehigh-concentration regions 13 are formed.

As depicted in FIG. 65, when the LOCOS oxide films 66 are formed in theactive portion in FIG. 54, LOCOS oxide films 67 are simultaneouslyformed on the p-type high-concentration regions 13 using the openings57.

As depicted in FIG. 66, when the nitride film of the active portion isremoved and the p regions 17 are formed in FIG. 55, the nitride film issimultaneously removed and the p regions 17 are simultaneously formed inthe surface layer of the n⁻ drift layer 2 using the LOCOS oxide films 67as a mask.

As depicted in FIG. 67, when the gate insulting film 3 a, the gateelectrodes 9, and the n source regions 11 are formed in the activeportion in FIG. 56, the gate insulating film 3 a not depicted, the gateelectrodes 9, and the n source regions 11 are simultaneously formed.When the gate electrodes 9 are formed, the second mask to form the gateelectrodes 9 in the active portion is used. For example, the gateelectrodes 9 are formed such that the gate electrodes 9 cover the threeLOCOS oxide films 67 of the four LOCOS oxide films 67 formed on the onen counter layer 7. The n source regions 11 are formed by implantingn-type impurity ions using the LOCOS oxide films 67 not covered by thegate electrodes and the gate electrodes 9 as a mask.

As depicted in FIG. 68, when the LOCOS oxide films 64 in the activeportion are removed in FIG. 57, the LOCOS oxide films 67 not covered bythe gate electrodes 9 are removed. By doing this, the LOCOS oxide films67 covered by the gate electrodes 9 are left on the p-typehigh-concentration regions 13. When the insulating film 12 is formed andetched in the active portion, an insulating film 19 is simultaneouslyformed and etched. At this time, though all the gate electrodes 9 do notneed to be covered, the gate electrodes 9 are caused to be almostcovered.

As depicted in FIG. 69, when the source electrode 14 is formed in FIG.58: an Al—Si film is deposited on the anterior side of the semiconductorsubstrate; Al—Si film separation is executed; and thereby, the sourceelectrode 14 is formed. The source electrode 14 commonly contacts thep-type high-concentration regions 13 and the n source regions 11 in theopenings 58. Different from the active portion, the source electrode 14is adapted to contact a portion of each of the gate electrodes 9 andthereby, its electric potential is fixed.

In the twelfth embodiment, the manufacturing method of one guard ring isdescribed. However, plurality of guard rings may be formed in thevoltage-resistant structure portion 200 according to the same method.When guard rings overlap with adjacent guard rings, the positions andthe width of the openings 56 depicted in FIG. 62 only have to be varied.

According to the twelfth embodiment, the ion implantation to form the p⁻well regions 10 of the active portion and that to form the p guard rings10 c in the voltage-resistant structure portion of the semiconductorapparatus can be simultaneously executed.

Thirteenth Embodiment

A voltage-resistant structure portion of a semiconductor apparatusaccording to a thirteenth embodiment will be described. FIG. 70 is across-sectional diagram of the voltage-resistant structure portion ofthe semiconductor apparatus according to the thirteenth embodiment. Asdepicted in FIG. 70, the voltage-resistant structure portion 200according to the thirteenth embodiment is provided, for example, on anouter edge of the active portion 100 of the semiconductor apparatusdepicted in FIG. 1. In the voltage-resistant structure portion 200, a p⁻off-set region 10 d (fifth semiconductor region) is provided in thesurface layer of the n⁻ drift layer 2, having a loop shape andsurrounding the p⁻ well regions 10. The p⁻ off-set region 10 d isconnected to the p⁻ well regions 10. The diffusion depth of the p⁻off-set region 10 d is deeper than the diffusion depth of the p⁻ wellregions 10.

The p⁻ off-set region 10 d has the impurity concentration higher thanthat of the n⁻ drift layer 2 and lower than that of the p⁻ well regions10. A plurality of p⁻ off-set regions 10 d may be provided. In thiscase, the adjacent p⁻ off-set regions 10 d are disposed to contact eachother. By providing the p⁻ off-set regions 10 d in this manner, a diodestructure (see FIG. 101) for current clipping that is configured by thep⁻ well regions 10 and the n-type high-concentration regions 13 in theconventional semiconductor apparatus can be configured by the p⁻ off-setregion 10 d and the p-type high-concentration regions 13.

A p⁻ region 10 b (sixth semiconductor region) is provided having a loopshape and surrounding the p⁻ off-set region 10 d. The p⁻ region 10 b isconnected to the p⁻ off-set region 10 d. The impurity concentration andthe diffusion depth of the p⁻ region 10 b are equal to those of the p⁻off-set region 10 d. The p guard rings 10 c (seventh semiconductorregion) are provided surrounding the p⁻ region 10 b and each having aloop shape. The edge of each of the p guard rings 10 c is connected tothe p⁻ region 10 b. The impurity concentration and the diffusion depthof the p guard rings 10 c are equal to those of the p⁻ off-set region 10d. The p⁻ off-set region 10 d, p⁻ region 10 b, and the p guard rings 10c are provided at the same impurity concentration and in the samediffusion depth.

On the outer circumference of the chip, a p stopper region 74 isprovided in the surface layer of the n⁻ drift layer 2. The p stopperregion 74 is connected to a stopper electrode 9 c and a metal film 14 bthrough the contact opening 76 provided in the insulating film.According to the planar structure not depicted of the chip that has thevoltage-resistant structure portion 200, an active portion 100 isprovided in the central portion of the chip and the voltage-resistantstructure portion 200 is disposed on the outer circumference of theactive portion 100 surrounding the active portion 100. The p stopperregion 74 and the contact opening 76 of the voltage-resistant structureportion 200 are provided over the entire circumference of thevoltage-resistant structure portion surrounding the p guard rings 10 con the outer circumference of the chip. Other configurations of thevoltage-resistant structure portion are same as those of thevoltage-resistant structure portion of the semiconductor apparatusdepicted in FIG. 60.

The cross-sectional structure of active portion vicinity 202 of thevoltage-resistant structure portion 200 will be described with referenceto FIG. 71. FIG. 71 is a diagram for explaining the cross-sectionalstructure of the active portion vicinity of the voltage-resistantstructure portion 200 depicted in FIG. 70. On the outer edge of theactive portion, the p-type high-concentration regions 13 are selectivelyprovided in the regions that are sandwiched by the n source regions 11and the p⁻ off-set region 10 d in the surface layer of the p⁻ wellregions 10. Other configurations in the active portion are same as thoseof the active portion 100 of the semiconductor apparatus depicted inFIG. 1.

On the inner circumference of the voltage-resistant structure portion200, first local oxide films 261 are selectively provided in the surfacelayers of the p⁻ off-set region 10 d, the p″ region 10 b, and the pguard rings 10 c. The p-type high-concentration regions 13 are providedin the surface layer of the p⁻ off-set region 10 d and the p guard rings10 c that are exposed between the adjacent first local oxide films 261.The p-type high-concentration regions 13 have the impurity concentrationhigher than that of the p⁻ well regions 10. In the surface layer of theoverlapping points 23 of the p⁻ region 10 b and the p guard rings 10 c,second local oxide films 262 are disposed to connect to each other thefirst local oxide films 261 adjacent to each other sandwiching theoverlapping points 23.

A first field plate electrode 9 a (first conductive layer) is providedhaving a loop shape on the p⁻ region 10 b through the first local oxidefilms 261. A second field plate electrode 9 b (second conductive layer)is provided having a loop shape and surrounding the first field plateelectrode 9 a, on the overlapping points 23 of the p⁻ region 10 b andthe p guard rings 10 c through the second local oxide films 262. Thesecond field plate electrode 9 b is apart from the first field plateelectrode 9 a.

Preferably, the second field plate electrode 9 b is disposed to cover atleast a portion of the p⁻ region 10 b. The spacing between the firstfield plate electrode 9 a and the second field plate electrode 9 b maybe, for example, 5 micrometers. The second field plate electrode 9 b maybe provided straddling the first local oxide films 261 that is connectedto the second local oxide films 262 on the p guard rings 10 c.

By providing the first and the second field plate electrodes 9 a and 9 bas described, the electric field intensity generated in thesemiconductor substrate can be reduced. The reason thereof will bedescribed later. The first and the second field plate electrodes 9 a and9 b may be made of poly-silicon that is added with first-conductivityimpurities (doped poly-silicon).

On the first and the second field plate electrodes 9 a and 9 b, theinter-layer insulating film 19 (third insulating film) is selectivelydisposed to expose a portion of the second field plate electrode 9 b. Onthe p⁻ region 10 b, a metal film 14 c is disposed on the inter-layerinsulating film 19 disposed on the first field plate electrode 9 a. Thefirst field plate electrode 9 a is at the source potential and the metalfilm 14 c is at the gate potential. On the p guard rings 10 c, thesecond field plate electrode 9 b and the metal films 14 a (thirdelectrode) that contacts the p-type high-concentration regions 13provided in the surface layer of the p guard rings 10 c are provided. Asdescribed, the metal films 14 a are disposed on the semiconductorsubstrate contacting the second field plate electrode 9 b. The p-typehigh-concentration regions 13 provided in the surface layer of the p⁻off-set region 10 d are connected to the source electrode 14 that isdisposed on the active portion. On the source electrode 14 and the metalfilms 14 a and 14 c, the protective film 15 is disposed to separate thesource electrode 14 and the metal films 14 a and 14 c from each other.On the posterior side of the n-type low-resistance layer 1, the drainelectrode 16 is provided.

On the overlapping points 23 (see FIG. 70) between the plurality of pguard rings 10 c disposed toward the outer circumference of the chip,the first and the second field plate electrodes 9 a and 9 b are providedsimilarly to the regions on the overlapping points 23 of the p⁻ region10 b and the p guard rings 10 c. As described, on the regions betweenthe adjacent p guard rings 10 c, the first and the second field plateelectrodes 9 a and 9 b are provided and thereby, the same effects can beobtained as those of the case where the first and the second field plateelectrodes 9 a and 9 b are provided between the p⁻ region 10 b and the pguard rings 10 c.

A manufacturing method of the voltage-resistant structure portion of thesemiconductor apparatus according to the thirteenth embodiment will bedescribed. FIGS. 72 to 83 are diagrams for sequentially explaining themanufacturing method of the voltage-resistant structure portion of thesemiconductor apparatus according to the thirteenth embodiment. Themanufacturing processes of the voltage-resistant structure portion 200are simultaneously executed, for example, with the formation of theactive portion 100 depicted in FIG. 1.

As depicted in FIG. 72, similarly to the first embodiment, the n⁻ driftlayer 2, the screen oxide film 3, and the nitride film 4 are depositedin this order on the anterior side of the n-type low-resistance layer 1.These processes are simultaneously executed when, for example, the n⁻drift layer 2, the screen oxide film 3, and the nitride film 4 aredeposited on the active portion in FIG. 2. In this case, the thicknessof the nitride film 4 merely has to be a thickness of which ions by theion implantation described later do not penetrate the nitride film 4 andmay be about several thousand angstroms. When the ions are implantedfrom above a resist film formed on the nitride film 4, the resist filmmerely has to be formed to have the thickness of which the ions do notpenetrate the resist film and the thickness of the nitride film 4 may bethin.

As depicted in FIG. 73, the nitride film 4 is etched by photo-etchingusing the sixth mask not depicted and formed by pattern-forming with aresist film using a photo-mask and thereby, a nitride shielding film 241is formed. Thereby, a first shielding opening 251 having the n⁻ driftlayer 2 exposed therein through the screen oxide film 3 and havingexposed therein a region to form therein the p⁻ off-set region 10 d; asecond shielding opening 252 having exposed therein a region to formtherein the p⁻ region 10 b; and a third shielding opening 253 havingexposed therein a regions to form therein the p guard rings 10 c, areformed.

The first, the second, and the third shielding openings 251, 252, and253 are each formed to have a loop shape. The second shielding opening252 is formed to surround the first shielding opening 251. The thirdshielding opening 253 is formed to surround the second shielding opening252. A plurality of first shielding openings 251 may be formed. Aplurality of third shielding openings 253 may be formed.

The width of a nitride shielding film 241 that partitions between thefirst and the second shielding openings 251 and 252 is designed to be awidth through which the p⁻ off-set region 10 d and the p⁻ region 10 bare connected to each other by thermal diffusion. The width of the firstshielding opening 251 is designed to be a width by which the p⁻ off-setregion 10 d can be formed having a size with which the amount ofavalanche resisted is not reduced by the p-type high-concentrationregions 13 formed in the surface layer of the p⁻ off-set region 10 d.

The width of the nitride shielding film 241 that partitions between thesecond and the third shielding openings 252 and 253 is designed to be awidth through which the p⁻ region 10 b and the p guard rings 10 c areconnected to each other by thermal diffusion. When the plurality of p⁻off-set regions 10 d are formed, a plurality of first shielding openings251 are formed and the width of the nitride shielding film 241 thatpartitions between the first shielding openings 251 is designed to be awidth through which the p⁻ off-set regions 10 d are connected by thermaldiffusion.

A region formed by a plurality of diffusion regions formed in adjacentthird shielding openings 253 and connected to each other by thermaldiffusion may be each one p guard ring 10 c. More specifically, forexample, a region formed by diffusion regions formed in adjacent twothird shielding openings 253 and connected to each other may be each onep guard ring 10 c (see FIG. 70). When a region formed by pluraldiffusion regions connected to each other is each one p guard ring 10 cas described and plural p guard rings 10 c are formed, more thirdshielding openings 253 are formed. In this case, the width of thenitride shielding film 241 positioned on a region to be formed thereinthe overlapping point 23 between the adjacent p guard rings 10 c isdesigned such that the connecting portion caused by the thermaldiffusion of the p guard rings 10 c becomes gradually smaller toward theouter circumference of the chip. The width of the nitride shielding film241 is designed such that the p guard rings 10 c are not connected toeach other by the thermal diffusion on the outer edge of the chip.

As depicted in FIG. 74, ions are implanted into the first, the second,and the third shielding openings 251, 252, and 253 and are thermallydiffused and thereby, the p⁻ off-set region 10 d is formed in thesurface layer of the n⁻ drift layer 2 that is exposed in the firstshielding opening 251. The p⁻ region 10 b is formed in the surface layerof the n drift layer 2 that is exposed in the second shielding opening252. The p guard ring 10 c is formed in the surface layer of the n⁻drift layer 2 that is exposed in the third shielding opening 253. Atthis time, the ion implantation may be executed at an acceleratingvoltage of 45 keV, with a dose of about 10¹²/cm², and using boron (B) asthe dopant. Due to this process, the p⁻ off-set region 10 d, the p⁻region 10 b, and the p guard ring 10 c are formed at the impurityconcentration higher than that of the n⁻ drift layer 2 and lower thanthat of the p⁻ well regions 10 formed in a process described later.Thereby, the p⁻ off-set region 10 d, the p⁻ region 10 b, and the regionsbetween the p guard rings 10 c tend to be depleted and therefore, thevoltage resistance of the semiconductor apparatus can be improved.

As depicted in FIG. 75, using the nitride shielding film 241 as a mask,the first local oxide films 261 such as LOCOS are selectively formed bythermal oxidation in the surface layers of the p⁻ off-set region 10 dexposed in the first shielding opening 251, the p⁻ region 10 b exposedin the second shielding opening 252, and the p guard rings 10 c exposedin the third shielding opening 253. The first local oxide films 261 aregrown to have a thickness of, for example, about 8,000 angstrom.

As depicted in FIG. 76, the nitride shielding film 241 is selectivelyremoved. Thereby, the nitride shielding film 241 is left only in theregions to be formed with the p⁻ well regions 10, that is, the activeportion (see the nitride film 4 of FIG. 2). Between the nitrideshielding film 241 and the first local oxide film 261, a portion of eachof the p⁻ off-set region 10 d, the p⁻ region 10 b, and the p guard rings10 c is exposed through the screen oxide film 3.

As depicted in FIG. 77, using the nitride shielding film 241 and thefirst local oxide films 261 as a mask, the second local oxide film 262is selectively formed by thermal oxidation in the surface layers of thep⁻ off-set region 10 d, the p⁻ region 10 b, and the p guard rings 10 c.The second local oxide film 262 is grown to have a thickness of, forexample, about 4,000 angstrom. In this case, the thickness of the secondlocal oxide film 262 merely has to be a thickness of which ions by theion implantation described later do not penetrate the second local oxidefilm 262 and may be about several thousand angstroms. The nitrideshielding film 241 is removed using a seventh mask not depicted andformed by pattern-forming with a resist film using a photo-mask. Thisprocess is simultaneously executed when, for example, the nitrideshielding film 61 is formed in the active portion in FIG. 3. The seventhmask is simultaneously used with the first mask used for the manufactureof the active portion.

As depicted in FIG. 78, when the n counter layer 7 is formed in theactive portion in FIG. 4, the n counter layer 7 is simultaneously formedby implanting n-type impurity ions at the impurity concentration higherthan that of the n⁻ drift layer 2 using the first and the second localshielding oxide films 261 and 262 as a mask. By doing this, the ncounter layer 7 is formed to contact the region of the p⁻ off-set region10 d on its active portion side of the innermost circumference. In theion implantation in this process, impurity ions are implanted at theimpurity concentration higher than that of the n⁻ drift layer 2.

In this case, the n counter layer 7 may and may not be formed. However,by forming the n counter layer 7, the WET resistance of the p⁻ wellregions 10 may be reduced similarly to the first embodiment. In thesurface layer of the semiconductor substrate, by using the first and thesecond local shielding oxide films 261 and 262 as a mask, in the regionsimmediately beneath the local oxide films, the n-type impurityconcentration is lower than that of the n counter layer 7. Therefore,the same effects as those of the first embodiment can be obtained. Thevoltage-resistant structure portion can be adapted not to obstructdiffusion of impurities from the p⁻ off-set region 10 d formedimmediately beneath the local oxide films to other regions.

As depicted in FIG. 79, similarly to the first embodiment, the screenoxide film is removed and the gate insulating film 3 a and thepoly-silicon 8 are formed in this order on the anterior side of thesemiconductor substrate. This process is simultaneously executed when,for example, the gate insulating film 3 a and the poly-silicon 8 areformed in the active portion in FIG. 5. At this time, similarly to thefirst embodiment, during the growth of the poly-silicon 8 or after thegrowth of the poly-silicon 8, the poly-silicon 8 is caused to become then type by doping n-type impurities such as phosphorus thereinto.

As depicted in FIG. 80, similarly to the first embodiment, thepoly-silicon is selectively etched using an eighth mask not depicted andformed by pattern-forming with a resist film using a photo mask. Thisprocess is simultaneously executed when, for example, the gateelectrodes 9 are formed in the active portion in FIG. 6. The eighth maskis simultaneously used with the second mask used in the manufacture ofthe active portion.

Due to this process, in the active portion 100, the gate electrodes 9are formed through the gate insulating film 3 a on the n counter layer7. In the voltage-resistant structure portion 200, the first field plateelectrode 9 a is formed through the first local oxide films 261 on thep⁻ region 10 b. The second field plate electrode 9 b is formed throughthe second local oxide films 262 on the overlapping points 23 of the p⁻region 10 b and the p guard rings 10 c. The first and the second fieldplate electrodes 9 a and 9 b are also formed on regions between the pguard rings 10 c formed toward the outer edge of the chip.

As depicted in FIG. 81, similarly to the first embodiment, the p⁻ wellregions 10 and the n source regions 11 are sequentially formed in thisorder using the gate electrodes 9 and the first and the second localoxide films 261 and 262 as a mask. Due to this process, the p⁻ wellregions 10 is formed in the surface layer of the n counter layer 7 topenetrate the n counter layer 7 and reach the n⁻ drift layer 2. Thisprocess is simultaneously executed when, for example, the p⁻ wellregions 10 and the n source regions 11 are formed in the active portionin FIG. 7.

As depicted in FIG. 82, the insulating film 19 is formed on the anteriorside of the semiconductor substrate. The insulating film 19 isselectively etched using a ninth mask not depicted and formed bypattern-forming with a resist film using a photo mask and,simultaneously, the second local oxide films 262 exposed on the anteriorside of the semiconductor substrate are removed. At this time, theinsulating film 12 is removed such that the insulating film 12 coversthe gate electrodes 9 and the region that is sandwiched by the n sourceregions 11 of the p⁻ well regions 10, and a portion of each of the nsource regions 11 are exposed. The insulating film 19 is removed suchthat a portion of the second field plate electrode 9 b is exposed. Thisprocess is simultaneously executed when, for example, the insulatingfilm 12 is formed in the active portion in FIG. 8. The ninth mask issimultaneously used with the third mask used in the manufacture of theactive portion.

As depicted in FIG. 83, using the insulating films 12 and 19, the firstfield plate electrode 9 a, and the first local oxide films 261 as amask, similarly to the first embodiment, p-type impurity ions areimplanted at the impurity concentration higher than that of the p⁻ wellregions 10 and an annealing process is applied to the extent that theions do not diffuse to regions immediately beneath the gate electrodes 9and thereby, the p-type high-concentration regions 13 are formed in thesurface layers of the p⁻ well regions 10, the p⁻ off-set region 10 d,and the p guard rings 10 c. By forming the p-type high-concentrationregions 13 in this manner, latching up can be prevented similarly to thefirst embodiment. This process is simultaneously executed when, forexample, the p-type high-concentration regions 13 are formed in theactive portion in FIG. 9.

As depicted in FIG. 71, similarly to the first embodiment, Al—Si isdeposited on the anterior side of the semiconductor substrate and Al—Siseparation is executed in a region not depicted and thereby, the sourceelectrode 14 and the metal films 14 a and 14 c are formed. At this time,though not depicted, the metal film contacting the stopper electrode isalso simultaneously formed. The protective film 15 is formed on thesource electrode 14 and the metal films 14 a and 14 c. The drainelectrode 16 is formed on the posterior side of the semiconductorsubstrate. In this manner, the semiconductor apparatus according to thethirteenth embodiment is completed.

FIG. 84 is a cross-sectional diagram of the equi-potential linedistribution generated in the semiconductor apparatus depicted in FIG.71. The equi-potential line distribution depicted in FIG. 84 isequi-potential line distribution obtained using two-dimensionalsimulation (same in FIG. 91 below). As depicted in FIG. 84, in thevoltage-resistant structure portion 200, equi-potential lines extendfrom the spacing 22 between the first and the second field plateelectrodes 9 a and 9 b toward the outside of the semiconductorsubstrate. The equi-potential lines inflate toward the outercircumference of the chip at a p-n junction region 231 beneath thespacing 221 and the intervals therebetween are widened. As described, itcan be seen for the semiconductor apparatus according to the thirteenthembodiment that the electric field intensity is low in the p-n junctionregion 231. Thereby, in the semiconductor apparatus according to thethirteenth embodiment, the same voltage resistance can be maintainedeven when the p guard ring formation region is shortened. Therefore,finer processing of the semiconductor apparatus can be facilitated.

Though not depicted, it has been seen that, in the semiconductorapparatus according to the thirteenth embodiment, the electric fieldintensity in the vicinity of the surface of the n⁻ drift layer 2 becomesstronger toward the outer edge of the chip, the cause of which may beinferred to be that before depleted layers formed around the p⁻ wellregions 10, each of which is the main junction are broken down by anavalanche, the depleted layers extend toward the outer edge of the chipto the adjacent p⁻ off-set region 10 d, the p region 10 b, and the pguard rings 10 c. It has been seen that the electric field intensity inthe vicinity of the p-n junctions between the n⁻ drift layer 2, and thep⁻ off-set region 10 d, the p⁻ region 10 b, and the p guard rings 10 cbecome lower toward the outer edge of the chip. It is estimated as thereason thereof that the electric field intensity in the vicinity of thep-n junction is mitigated by the extending of the equi-potential linesin the semiconductor substrate from a plural pieces of spacing 221disposed on the anterior side of the semiconductor substrate toward theoutside.

Based on the above description, according to the thirteenth embodiment,similarly to the first embodiment, the number of photo-masks used duringthe manufacturing processes in the active portion can be reduced by onerelative to that of the conventional manufacturing processes. Associatedwith this, in the voltage-resistant structure portion simultaneouslyformed, the number of masks used during the manufacturing processes canalso be reduced by one relative to that of the conventionalmanufacturing processes. Even when the number of masks used during themanufacturing processes is reduced by one relative to that of theconventional manufacturing processes, the semiconductor apparatus havingthe same performance as that of the conventional semiconductor apparatuscan be manufactured. Thereby, the effects same as those of the firstembodiment can be obtained. The manufacturing cost can be reduced. Thenumber of times to use the photo-masks can be reduced and thereby,degradation can be prevented of the alignment precision caused by theaccumulation of the mask misalignment errors generated in each exposureof a pattern and therefore, variation among devices caused during theirmanufacture can be reduced. The number of heat treatment sessionsexecuted from the formation of the gate electrodes and the field plateelectrodes to the formation of the inter-layer insulating film can bereduced and therefore, production of bird's beaks can be prevented.According to the thirteenth embodiment, the first and the second fieldplate electrodes 9 a and 9 b are provided as described and thereby, theelectric field in, for example, the p-n junction region 231 configuredby the p guard rings 10 c and the n⁻ drift layer 2 can be mitigated.Therefore, the electric field intensity generated in the semiconductorsubstrate can be reduced when the semiconductor apparatus is turned on.Thereby, even when finer processing of the semiconductor apparatus isfacilitated, the same voltage resistance as that of the conventionalsemiconductor apparatus can be maintained.

Fourteenth Embodiment

A manufacturing method of a semiconductor apparatus according to afourteenth embodiment will be described. FIG. 85 is a cross-sectionaldiagram of a voltage-resistant structure portion of the semiconductorapparatus according to the fourteenth embodiment. FIG. 86 is a diagramfor explaining the cross-sectional structure of the active portionvicinity 202 of the voltage-resistant structure portion 200 depicted inFIG. 85. As depicted in FIGS. 85 and 86, in the voltage-resistantstructure portion 200 of the semiconductor apparatus according to thefourteenth embodiment, the second field plate electrode 9 b may beformed using a metal.

As depicted in FIG. 86, the second field plate electrode 9 b is formedonly on the first local oxide film 261 provided in the surface layer ofthe p guard ring 10 c. The second field plate electrode 9 b is notformed on the second local oxide film 262 on the overlapping point 23 ofthe p⁻ region 10 b and the p guard ring 10 c. The second field plateelectrode 9 b may be provided as a metal layer.

Preferably, the metal films 14 a formed on the p guard rings 10 c areprovided such that an end of each of the metal films 14 a on its activeportion side covers a portion of the p region 10 b. Other configurationsare same as those of the semiconductor apparatus according to thethirteenth embodiment.

A manufacturing method of the voltage-resistant structure portion of thesemiconductor apparatus according to the fourteenth embodiment will bedescribed. FIGS. 87 to 90 are diagrams for sequentially explaining themanufacturing method of the voltage-resistant structure portion of thesemiconductor apparatus according to the fourteenth embodiment. Themanufacturing processes of the voltage-resistant structure portion 200are simultaneously executed with, for example, the formation of theactive portion 100 depicted in FIG. 1.

Similarly to the thirteenth embodiment, the n⁻ drift layer 2, the ncounter layer 7, the p⁻ off-set region 10 d, the p⁻ region 10 b, the nguard rings 10 c, and the first and the second local oxide films 261 and262 are formed on the anterior side of the n-type low-resistance layer 1(see FIGS. 72 to 78). The gate insulating film 3 a and the poly-siliconare formed in this order on the anterior side of the semiconductorsubstrate (see FIG. 79).

As depicted in FIG. 87, similarly to the thirteenth embodiment, thepoly-silicon is selectively etched using the eighth mask not depictedand formed by pattern-forming with a resist film. Due to this process,similarly to the thirteenth embodiment, the gate electrodes 9 and thefirst field plate electrode 9 a are formed. The second field plateelectrode 9 b is formed through the first local oxide film 261 on the pguard rings 10 c. In the fourteenth embodiment, the second field plateelectrode 9 b is formed only on the first local oxide films 261 and isnot formed on the second local oxide films 262. The second field plateelectrode 9 b may be formed as a metal layer. In this case, afterforming the gate electrodes 9 and the first field plate electrode 9 a, aprocess of forming the second field plate electrode 9 b configured bythe metal layer is added.

As depicted in FIG. 88, similarly to the thirteenth embodiment, the p⁻well regions 10 and the n source regions 11 are sequentially formed inthis order in the surface layer of the n counter layer 7. As depicted inFIG. 89, similarly to the thirteenth embodiment, the insulating film 19is selectively formed on the anterior side of the semiconductorsubstrate and, simultaneously, the second local oxide films 262 exposedon the anterior side of the semiconductor substrate are removed.

As depicted in FIG. 90, similarly to the thirteenth embodiment, thep-type high-concentration regions 13 are formed in the surface layers ofthe p⁻ well regions 10, the p⁻ off-set region 10 d, and the p guardrings 10 c. As depicted in FIG. 86, similarly to the thirteenthembodiment, the source electrode 14, the metal films 14 a and 14 c, themetal film not depicted and contacting the stopper electrode, and theprotective film 15 are formed on the anterior side of the semiconductorsubstrate and the drain electrode 16 is formed on the posterior side ofthe semiconductor substrate. In this case, the metal film 14 a formed onthe p guard rings 10 c is formed to cover a portion of the p⁻ region 10b. In this manner, the semiconductor apparatus according to thefourteenth embodiment 14 is completed.

FIG. 91 is a cross-sectional diagram of the equi-potential linedistribution generated in the semiconductor apparatus depicted in FIG.86. As depicted in FIG. 91, in the voltage-resistant structure portion200, the equi-potential lines extend from a spacing 222 between thefirst field plate electrode 9 a, and an end of the metal film 14 a onits active portion side formed on the overlapping points 23 of the p⁻region 10 b and the p guard rings 10 c, toward the outside of thesemiconductor substrate. The equi-potential lines inflate toward theouter circumference of the chip at a p-n junction region 232 beneath thespacing 222 and the intervals therebetween are widened. As described, itcan be seen for the semiconductor apparatus according to the fourteenthembodiment that the electric field intensity is low in the p-n junctionregion 232. Thereby, according to the semiconductor apparatus accordingto the fourteenth embodiment, the same effects as those of thesemiconductor apparatus according to the thirteenth embodiment can beobtained.

Based on the above description, according to the fourteenth embodiment,the same effects as those of the thirteenth embodiment can be obtained.

Examples of applying the present invention to a vertical MOSFET havebeen described in the first to the fourteenth embodiments. However, theapplication is not limited to the above. For example, the presentinvention may be applied to a voltage-resistant structure portion of apower IGBT. In this case, the n source regions 11 become emitter regionsand n drain regions not depicted become p collector regions (fourthsemiconductor regions). The first to the fourteenth embodiments may beapplied to a diode or a thyristor. When any of the embodiments isapplied to a diode: the MOS gate portion and the p⁻ well regions 10 arenot necessary; the n source regions 11 become n cathode regions; and then drain regions not depicted become p anode regions. When any of theembodiments is applied to a thyristor: the MOS gate portion is notnecessary; the n source regions 11 become n cathode regions; the n drainregions not depicted become p anode regions; and the p⁻ well regions 10become p base regions. In this case, gate electrodes only have to beformed in the p base regions.

INDUSTRIAL APPLICABILITY

As described, the manufacturing method of a semiconductor apparatus anda semiconductor apparatus according to the present invention are usefulfor manufacturing a high-power semiconductor apparatus and areespecially suitable for manufacturing a MOS semiconductor apparatus suchas a MOSFET or an IGBT.

REFERENCE SIGNS LIST

-   1 n-type low resistance layer-   2 n⁻ drift layer-   3 a gate insulating film-   7 n counter layer-   9 gate electrode-   10 p⁻ well region-   11 n source region-   61 nitride shielding film

The invention claimed is:
 1. A manufacturing method of a semiconductorapparatus, comprising: forming a first insulating film on a top side ofa substrate having a first semiconductor region of a first conductivity;selectively forming a shielding film element through an opening in thefirst insulating film; forming a control electrode on the firstinsulating film, apart from the shielding film element; forming a secondsemiconductor region of a second conductivity in the first semiconductorregion using the shielding film element and the control electrode as amask and selectively forming a third semiconductor region of the firstconductivity in a surface layer of the second semiconductor region usingagain the shielding film and the control electrode as the mask; forminga second insulating film to cover the control electrode and removing theshielding film element; forming a first electrode to contact the thirdsemiconductor region and to be insulated from the control electrode bythe second insulating film; and forming a second electrode on a side ofthe substrate, wherein at least a portion of the control electrode isdisposed over a part of the second semiconductor region that issandwiched between the first semiconductor region and the thirdsemiconductor region.
 2. The manufacturing method of claim 1, furthercomprising: forming a counter region of the first conductivity in thesurface layer of the first semiconductor region by implanting, throughthe shielding film element, impurity ions of the first conductivity atan impurity concentration greater than that of the first semiconductorregion, the counter region being formed after forming the shielding filmelement, wherein the second semiconductor region is formed in a surfacelayer of the counter region in the first semiconductor region, andwherein the at least a portion of the control electrode is disposed overa part of the second semiconductor region that is sandwiched between thecounter region in the first semiconductor region and the thirdsemiconductor region.
 3. The manufacturing method of claim 1, whereinthe shielding film element is an element made from a nitride film. 4.The manufacturing method of claim 1, wherein the shielding film elementis an element formed using an oxide film produced by chemical vapordeposition.
 5. The manufacturing method of claim 1, wherein theshielding film element is an element formed using an oxide film producedby thermal oxidation.
 6. The manufacturing method of claim 4, furthercomprising: forming a shielding film from which the shielding filmelement is made; and removing the part of the shielding film, wherein atthe forming of the shielding film, the shielding film is formed suchthat at least a portion of the shielding film is disposed immediatelybeneath the control electrode, and wherein at the removing of theshielding film, the portion of the shielding film disposed immediatelybeneath the control electrode is not removed.
 7. The manufacturingmethod of claim 6, wherein at the forming of the shielding film, theshielding film is formed such that the portion of the shielding film isdisposed immediately beneath the control electrode and does not reachany edge of the second semiconductor region.
 8. The manufacturing methodof claim 6, wherein at the forming the shielding film, the shieldingfilm is formed such that the portion of the shielding film is disposedimmediately beneath the control electrode and reaches an edge of thesecond semiconductor region.
 9. The manufacturing method of claim 1,further comprising: forming a high concentration region of the secondconductivity by implanting impurity ions of the second conductivityusing an accelerating voltage that permits the impurity ions topenetrate the third semiconductor region, from the surface layer of thesecond semiconductor region using the second insulating film as a mask,after forming the second insulating film and removing the shieldingfilm.
 10. The manufacturing method of claim 9, wherein at the forming ofthe high concentration region of the second conductivity, regions wherethe high concentration region of the second conductivity is exposed andis not exposed on a surface of the second semiconductor region areformed using a common mask.
 11. The manufacturing method of claim 10,wherein the region where the high concentration region of the secondconductivity is not exposed on the surface of the second semiconductorregion is formed at one point in each line portion of a stripe-shapedplanar structure that is formed by the region where the highconcentration region of the second conductivity is exposed on thesurface of the second semiconductor region.
 12. The manufacturing methodof claim 10, wherein the region where the high concentration region ofthe second conductivity is not exposed on the surface of the secondsemiconductor region is formed at a plurality of points in each lineportion of a stripe-shaped planar structure that is formed by the regionwhere the high concentration region of the second conductivity isexposed on the surface of the second semiconductor region.
 13. Themanufacturing method of claim 10, wherein the region where the highconcentration region of the second conductivity is not exposed on thesurface of the second semiconductor region is formed at staggeredpositions in each line portion of a stripe-shaped planar structure thatis formed by the region where the high concentration region of thesecond conductivity is exposed on the surface of the secondsemiconductor region.
 14. The manufacturing method of claim 1, furthercomprising introducing impurities of the first conductivity into thecontrol electrode.
 15. The manufacturing method of claim 1, wherein afirst-conductivity low-resistance layer is provided between the firstsemiconductor region and the second electrode.
 16. The manufacturingmethod of claim 1, wherein a fourth semiconductor region of the secondconductive type is provided between the first semiconductor region andthe second electrode.
 17. The manufacturing method of claim 1, whereinthe shielding film element is a LOCOS (Local Oxidation of Silicon)element.
 18. A method for making a semiconductor apparatus, comprisingthe steps of: forming a screen oxide film on a substrate having a firstconductivity type; forming a nitride film on the screen oxide film;forming an opening in the screen oxide and nitride films; growing aLOCOS (Local Oxidation of Silicon) element in the opening; removing thenitride film; forming a control electrode on the screen oxide film at aposition spaced apart from the LOCOS element; injecting impurities of asecond conductivity type into the substrate, using the control electrodeand the LOCOS element as a mask, to form a well region; and injectingimpurities of the first conductivity type into the well region, usingagain the control electrode and the LOCOS element as a mask.
 19. Themethod of claim 18, further comprising the step of removing the LOCOSelement after impurities have been injected into the well region.